Hello. I'll start off because I'm new here, by letting you all know that I was employed as an Installer for just over 7 years. Hope I can help out here. In retuen all I'd like is some pointers on getting my ride to where I want it..... So you say you want to fiberglass. Well, I'm not one to back down from a DIY project, so here goes.
1) Yes, Polyester resin will work best for proper curing. Use a good quality resin. Don't cheap out. From what I know, it is available as "waxed" or "unwaxed". I' m guessing that from a standpoint of mould-releasability, that waxed might be better. Also pick up some "Mold-Release". It's a waxy blue compound that you rub on the mold....(or in my line of work, on the amp and subwoofer plugs). This should make separating your new super-cool and super-custom bumper a snap. You can get the MEKP catalyst tinted if you need to, but generally, if you're mixing follow the directions carefully. A capful or two is all you need in a 1.5L bucket. Make sure you really mix this stuff good, like about 3 minutes using a figure 8 motion and scraping the bottom. Worth noting, you should mix not more than you can use in a 10-15 minute period. When the resin starts to kick it will turn a darker brown and get like jelly. You'll know it's starting to harden when it gets warm to the touch and is no longer tacky.
I've gotten the best results from using 1" disposable brushes, Blue Latex gloves..(tattoo quality), some disposable containers(the jumbo-yogurt ones work best)and a respirator that has changeable cartridges and applying a thin layer of resin to the work surface to make the mat stick and then dab, not brush, the resin onto the pieces of mat so as to get any air bubbles out of the workpiece. (Air bubbles can cause vibration to amplify while driving and you might get a nasty crack in the paint.
Now, when it comes to the actual mat itself... you may want to get the thinner stuff because you'll need to tear it into workable chunks(use gloves when doing this and get your self a big ol' cardboard box). The reason you tear this stuff is so that when you are "glassing" that all the edges mesh nicely without any big ridges. This is important for when you do the next layers. Start off with about a layer of 2-3 pieces thick. Let it cure. If you try to do it too thick, there's a chance that the heat created during the curing will be enough to warp the mould.
(Break for a six-pack with your buddies here and show them the cool stuff you just made with your own hands)
OK! Back to work, slacker!
Now that your mould is all hard and dry(not