Powder coating is a valid option if they are perfect, however every flaw in the metal will show if they have any. If repairs have been made and any kind of filler has been used powder coating is a bad idea. Also, powder coating looks nice/even but does not look O.E. correct so if that matters in your case I'd advise against it. Paint brand is less important than prep and application of the paint
Start with CLEAN bare metal, no primer, and warm the covers in an oven or sunlight (not hot, just warm, 100-120F or so is plenty). Shake cans for several minutes (have at least 3-4 cans handy for a pair) apply first coat evenly and fairly heavy, its a tightrope as its easy to get runs and sags so go easy (I'd buy a spare can to practice on a junk cover first). Wait 10 full minutes and add a second coat, wait another 10 minutes and add a 3rd coat, all as even and as heavy as you dare short of runs or sags (sags can take a while to show so you really need to be careful). Once coated let them dry for several days before handling as the paint stays gummy longer than you might think and can mark easily so dont let them rest against anything. Originals usually has some small runs and sags so dont worry if you get a few small ones. If they sag or run a bunch, more paint wont fix the issue, you'll need to strip them and start over. .02