Good morning,

I'm working on a a small plug which is about 20" by 25" by 8" deep. Photo hopefully attached. I am planning on sealing the mdf with shellac, then coating it with Duratec. It would be simpler to roll it or brush it, unless that results in a lot of sanding. The downside to spraying (for me) is that I have to purchase a spray gun, and set up a lot of plastic sheeting to contain overspray. Also, I'm wondering if spraying the inside corners of a box shape will result in drips, and end up requiring just at much sanding as brushing it.

I'm a complete newb at this. This is the first plug I've made. In the picture, the white/black stripe is the window flange of a Jeep Wrangler hardtop. The part will be a box that inserts where the window used to be. Later, a hinged cover will be made for the box. 

Thank your for your thoughts on this.
 

It's going to spray much much much better than it brushes. It can be brushed, but it's not formulated for it so it's a bit thin and hard to get good coverage without it sagging so you tend to need to do a few thinner coats. Then it's easy to sand but it's not easy to get rid of brush strokes, so you again end up needing to do a bit of sanding/filling/sanding/filling/sanding etc. When spraying it actually lays down so well you often dont need to sand it at all unless you're keying for topcoats.

The good news is; it will spray through a Preval sprayer if you dont want to invest in a proper spray setup. Less overspray too. Wont lay down as nicely as a good gun will get it down, but it's easy to sand so orange peel is no problem.