For rivets, I use a regular silver sharpie. All you have to do is hold the pen straight up and point the tip down enough to put a dot down. Instant rivets. If you look at the stuff I have painted on my website, you'll see the effect.
To make bolts. Same way, but then you dip your toothpick into Testor's thinner. Just enough to make it a dab wet and turn the rivet into a nut with 6 sides.
Key locks are just a round cut piece of masking tape with an exacto knife, place it where you want the lock, paint the shell, remove the tape, paint that, let dry, scribe a slot with Sharp toothpick, back with black.
Painting a grill with slots... cut out fine lines of masking tape on a piece of scrap lexan, take the tip of your exacto knife to one end and toothpick to the other end. Carefully place each strip in place, tap along areas of mask to hold it to the body, paint with chrome, remove strips, back with black. If you want to assure you have straight lines and equal spaces, use a metal rule and a fine tip sharpie on the outside of the area to be painted.