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.
 

I have recently had some great results with brushing Duratec sunshield with just a little MEK thinner. I think less than 5%.
It brushes thick enough and still flows out quite smooth.