How best to paint a radiator cover?

[northender]

OK we economised by getting a rad cover that needs painting. It has 2 of those patterned cut out mdf panels. dh is having a nightmare painting in the cut out bits iyswim and so we wondered if anyone has any tips. At this rate it'll take another 2 months to finish

Put it OUTSIDE on newspaper and spray it with PlastiDecor. Or a spray paint that will spray onto the existing substrate without cracking.