My plug is done and I'm about ready to lay up a mold. This will be used for prepreg so I'm using premium resin tech rdr-1902 high temp surface coat and rdr-3212 resin. I have some concerns with the surface coat. It's a bit thicker than I imagined but I guess that's good so it won't run, however after mixing a small test batch, it seems pretty slow to release air bubbles. As you can see in the pic of my plug, there are areas with vertical walls and even a few areas of negative angle. For air to release from the surface coat as I brush it on, these bubbles need to rise to the surface to pop right? So any areas that are beyond vertical with a negative angle, I would think are gonna have a hard time releasing air. I picture a bubble just rising up against the surface of the plug and staying there. I'm wondering if I should apply the surface coat in partial areas with the plug oriented so surface coat I'm applying is face up, allowing better release of air bubbles.  Do I need to bother? Or can I just brush it on the whole thing as it sits in the pic? Looks like pics got rotated 90 degrees, the pointed nose is up

Sounds good, i think ill just go for it. I have way more high temp coat and epoxy than i need so if i have to try more than once im just using up stuff thats gonna expire anyway. 

Yeh most epoxy surface coats are very thixotropic like that. The general technique is to cut the bristles on your brush to about 1" long, so they are quite stiff. Remember to pull the bristles a bit after to get rid of any loose ones. Then brush on a very thin coat, especially in corners, so that you dont trap any air on the surface. From there you can apply a heavier coat, and unless you go really over the top (which wont feel logical, so you won't), porosity shouldn't be an issue.

Done with the first coat. It's very hard to get this stuff to brush on thin. The brush just grabs and stops. Did my best and I'm pretty confident there's no air. I could see a few little bumps at first but they eventually popped and it's all leveled out nicely now. After this cures to just tacky I'll do another nice thick layer, let it tack, move on to lay up. The epoxy and surface coat says 24 hour cure. Should I let it go longer than that before pulling the plug and moving on to post cure? Would 2 or 3 days be better? 
Next part im a bit nervous about is getting this plug out of the mold. Its kind of hard to tell from the shape if it will or not. If it won't, I do have a back up plan. On the second pic you can see some scored lines on the plug. These are the trim lines for the final part. They will transfer to mold, then to part and give me a guide for trimming. Prepreg will only overlap those lines slightly. This means I can cut a slit in the mold along the back from about the middle to the back edge allowing the mold to spread a bit at the back to come off the plug. I can then fill that slit afterwards just to seal it. Prepreg won't be layed over that area. The reason I did the flange around the bottom is for bagging purposes. I want to try and just tack tape the bagging material to that flange rather than a full envelope. If this works, I can put a vacuum fitting in the top of the mold and not have to bother with a vacuum connector in the bagging material. Should make for a nice quick easy lay up of parts. 

I usually do a single thick application of surface coat. The areas I pay special attention to are sharp corners. Too thick in the corners and you do run the risk of trapping air. Otherwise, it should just need to be a single, thick application that wets out and self-levels. Once it tacks, the wet lay with the 3212 can begin. I usually give the mold 8 hours to cure then pop it off, trim, and post cure.

Whether you can pull it off depends on how thick you make the mold. Fiberglass or carbon? I would be wary of doing any additional laminating on the mold once it's removed from the plug. You're likely to see some warping if you go that route.

It's cf. The only reason I would have to do more laminating after removal is if I need to cut the slot to remove the mold. In that case, I'll probably just put a peice of tape over the slot on the inside, fill the crack with epoxy and maybe just one strip of laminate on outside. There will be no prepreg layed over that area in the mold. Just needs to be filled to seal vacuum if I end up using the flange for partial bag. I didn't go crazy with mold thickness.
Wow, only 8 hours? That's quick. You must have used quicker hardener than I did. For the 1902 surface coat I used 9302 hardener. For the 3212 epoxy I used 9386-99 hardener which has 1 hour pot life and 24 hour cure. There was an option for faster hardener with the epoxy, but I noticed the specs were drastically lower with the quick hardener. Tensile strength, etc. were much less. I'll give it at least 24 hours before popping it loose. 

Mold came out great. Not a single void in the surface. The dull spot you see up in the top is where I used some clay on the plug to smooth out an indentation that would would have made it more difficult to pull the plug out. Prepreg doesnt lay there so doesnt affect anything.  I did have to cut the slot to get the plug out, but no big deal. Adding the flange along the bottom for attaching a partial bag to was an interesting idea, but after messing with some bagging material last night, I don't think it's actually gonna be quicker than just an envelope. It requires a lot of pleats to allow enough material inside. Probably end up cutting off the flange. I think an envelope will also be more likely to be reusable. Now on to the post cure.

Another question before I start the post cure. My mold came out great and the gloss is as good as what I got on the duratec which is pretty good, but out of curiosity I tried hand polishing a small area up in the top and it was immediately obvious that this high temp surface coat will go to a brighter gloss than the duratec did. Is there any downside to polishing my mold now? Or should I just leave it alone? It's possible there's voids under the surface but I'm sure I wouldn't expose them just by polishing. 
If I do go ahead and polish the mold, should I do it before or after the post cure? I imagine it will polish easier now since the hardness will go up during cure, but will i lose some gloss during the cure? Should I polish afterwards?