Pinstripe would be an excellent choice for marking the fenders!!
Don't be scared! Just take your time and be careful when you're doing it. Look around the net, check out different fender cuts and pick something you really like, or come up with your own style. It's really easy, I was nervous the first time I did it, but I took my time and the outcome was better than expected!
Are you wanting true fire flames or classic flames? Sorry for asking so much, I just know a painter (the one who did mine) and he does a great job with single colors, etc. He can do flames, but I believe only classic flames. He doesn't airbrush, therefore can't do "true fire"