The center caps come loose when you take off the lug nuts.
I used Duplicolor matte black wheel paint, rattle can.
I just took the wheels off the van individually and painted them one by one.
I used 3m scuffing pads to thoroughly rough up the silver finish and then washed them with simple green, and wiped them down with a prepaint degreaser/cleaner just before painting.
Did the same with the center caps, the silver emblems on mine were very easy to get off, I just carefully pinched the little clips on the backside together and they slid out. I do believe this breaks the clips as they are thin plastic, so when I put mine back on after painting the caps I superglued the heck out of them inside & out, no probs yet.