There's a trick to getting mat to lay smooth and, therefore, take about 10 pounds less filler. First, use butcher paper to figure out patterns for the pieces of glass. Mat doesn't stretch/move/behave until it's wet, so the butcher paper makes good templates. Once you have that done, do the same for some 3/4 oz glass cloth and do your best to stagger the edges. Wet out the glass, lay it on the plug, and scrape off most of the resin. The surface of the cloth shouldn't be shiny. Now the fun part. Wrap the whole thing in the widest electrical tape you can find pulling it fairly tight. Once it's green (solid, but sticky) trim the edges, give it a bit longer and pull off the tape. Getting the plug out is a different story. I usually use EPS foam plugs covered in clear packing tape. Once the glass is cured I use whatever solvent is handy to disolve the foam out of the part, then pull out the tape. It makes a giant mess and stinks like the end of the world, but it works.
Done like that the outside surface will be fairly smooth and shouldn't need much filler. If you really want to go overboard and get a near perfect surface, vacuum bag it. I've made a few bagged parts and they needed zero filling and just a quick scuff and wipe with acetone to be ready for primer.
Mine- 2k TJ, RC 2.5 lift, .75 spacers, Soft 8s, 33" KM2s, winch, lights, and so on
Hers- 06 WK, bone stock until she leaves it and the credit card with me for an unsupervised weekend
You're the retarded offspring of five monkeys having butt sex with a fish-squirrel.