Here is what I do.
I use rattle can paint (brand not real important) and spray the tubes slid on an old coat hanger shaped pedestal and toss them into the toaster oven for 5 minutes. For the blanks, I throw one squirt into each hole and spread it around with a q-tip. Toss into the toaster oven for 5 minutes.
I started back painting by spraying the tubes/blanks and letting them dry over night. I am not very patient when it comes to that kind of waiting, so I went up to the Goodwill around the corner and bought my practically new toaster oven for $2.50. Granted, it was on sale that day for 50% off all white tags. BONUS!
I have tried the toaster oven method with acrylic paints, and they bubbled on the tubes. Not all of them, but one or two. Now, I stick with spray paint for every thing.
My .02