The brake calipers, you can use high temp paint, or powder coat (keeping the coating off the internals, threads, etc). Powder coat would probably hold up better as brake fluid can take off paint if left on long enough...
Re the forks, You can scruff and paint them as well BUT their likely going to get scuffed up as you reassemble them. Perhaps if SUPER CAREFUL, you can get them back in without scratching..
As long as the clamps are torqued to spec's, the paint won't make a difference.
You can always partially dis-assemble, tape off and paint the fork legs. If your super neat and very anal when taping, it should look ok.
I would use the BEST paint you can find...
*Truck bed lining paint, which is slightly textured, holds up very well,has a similar finish as stock lower legs.