Keep in mind I ETCHED the SC coating (OEM) with Castrol SuperClean and rinsed well, then doused with Acetone before painting it last march. That gave a good surface to bind to.
I would imagine scuffing up the UIM with some 120 grit or so, maybe even as fine as 220 would give a good surface for the stuff to stick to.
I have a spare UIM here. Want me to try it? Keep in mind, doing this on OEM valve covers won't accomplish much. The OEM valve covers are too much of an insulator to begin with. Cooling off that outer surface won't help a bit.