Hi, I've used decal flags and like all decals some are better than others. I normally just apply the decal around the line (after trimming/ cutting film as close to the flag as possible) and let it dry. Standing straight out -- whatever let it dry. At this point ,after it drys, I might attempt to trim any film, they are fragile and might shatter/fall apart, or paint any nicks in the decal -- it happens -- then after all is dry just touch the flag decal with the smallest drop of micro- sol you can get on a pin. let it dry, observe and re=apply the micro-sol if you need more "bending". don't ever touch the decal with your hands while dooing this. You might influence the bend one way or another with a toothpick while its wet, but its risky. Then when its dry again gently shoot the flag(s) with dullcoat. Their always gonna be brittle though.
good luck G.L.