VHT Wrinkle plus. I think I got it at O'Riellys, about 8-9 bucks a can.
I taped off the large aluminum area with painters tape and just sprayed over the ribs.
Once dry, I used a fine grit disk on on an angle die grinder and gently cleaned up the ribs.
Get two cans (one for each cover), when spraying it go end to end, again at an angle across the covers and again at at angle the opposite way if that makes sense without stopping between coats (be careful not to let it run). Let them sit in the sun to dry. I did one coat at first and it wouldn't wrinkle, so after some research I found that multiple coats at different angles was the way to go.