Cera/Duracoat questions

[fishuhalik]

Looking at getting 4 of my shotguns coated, a Beretta a391 eXtrema 2, 870 Wingmaster, 870 Express and 870 Express Youth 20 gauge. All guns are used almost exclusively in the salt, so they're being coated purely for functional reasons. The Beretta is my daily use gun, the 870 Youth is my sons gun and I may want to do some kind of pattern/camo on those, but the other 2 will be solid colors. Here's my questions
1. I've done some research and it looks pretty darn easy to do yourself, but I wonder how long a DIY project would hold up versus a professional job. Any of you guys done it and how have they held up after heavy use in salt water?
2. My biggest question. The Beretta has some surface rust that wiped clean but always returns, and the Wingmaster is pitted. Loaned it to a buddy and he left it in a wet case for 6 months before getting it back to me. Was my dad's gun and I'll never speak to the guy again, but that's another story. Anyways, should I sandblast the rusty guns before the coat is applied?
3. Can the trigger assembly be coated?
4. Advantages between Duracoating and Cerakoting? My barrel doesn't usually get too burned up, but every once in a while I'll take it to a skeet range and put a couple hundred rounds through it and warm her up pretty good. Dove hunts can get some pretty fast shooting too