Weathering scratches can be done a few ways. If you have a dark primer underneath, sometimes it's just enough to scuff up the surface paint with sandpaper or brillo pads to scratch down and let the dark show through. Other methods would just be painting the scratches, or a combination. There are a lot of youtube videos showing various techniques for it.
I just finished painting mine last night, and can add the following thoughts to mirror some people's thoughts previously. I used the standard Toreador Red and Sunburst Gold for the mains, and just a Ford Silver Metallic for those. I didn't have any issues with paint peeling, even with very suboptimal conditions - very cold, and sometimes even rainy levels of humidity outside. Since I didn't have a choice but to paint, I sprayed my primer on the parts indoors (yeah, don't do that. Pets start walking in circles after a while.. kidding, but seriously, don't do as I do). The paint did have flashing issues based on a) how much paint was left in the can, and b) the temperature. I found that some of the areas, I actually had to retouch with a quick burst over it once back inside when things had warmed up. Still nowhere near perfect and with a lot more prep time, and better conditions it would look really great.
Back to the peeling though: I didn't have the luxury of overnight cure times with most of the pieces. Many of them, were masked off for gold accents within a few hours of being laid down. I also only managed about 5-10 minutes between coats. The Perfect Match Dupilicor dried to the touch that fast. Surely not fully cured, but workable. I used blue painters tape from Wal-mart, which was about what, 3 bucks a roll? Zero issues at all. The only peel I got, which was only one speck, was after I switched to a different tape, and I was worried when I started laying it, as it felt way tackier than the Wal-mart brand. Sure enough, I did fleck off a tiny bit when peeling that back. It might not have been an issue with full cure times. But the cheap stuff worked well with crisp lines and no worries about peeling even with the rush job I did.
TLDR: give yourself enough prep time, and follow the directions, and you'll be fine.
Also, for my Mark 7 suit, I used:
Duplicolor Filler Primer - 2 cans
Duplicolor Perfect Match Toreador Red (8 oz) - 3 cans
Duplicolor Perfect Match Sunburst Gold Metallic (8oz) - 1 can
Duplicolor Perfect Match Silver Metallic (8oz) - 1 can
Duplicolor Perfect Match Clear Coat (8oz) - 2 cans
I only bought two cans of clear, and one went wonky after being cold, so plan accordingly. I ended up with 3-4 coats of paint on most pieces. I would've liked another coat of red at least on everything, but time crunch didn't allow, and no point really laying it on over sub-optimum prep anyway. The gold faceplate on the helmet got a couple extra coats though. I forgot to finish off the red at the top of mine after I cut it to remove, and ended up with overspray a little from that when I went back, even taped off. So I went back through and sanded it back down smooth and hit it with another couple of coats. Still enough Gold left for another layer on every gold accent, and the silver was barely touched.
