Chris asked about the CDs mentioned in an earlier post. Here is how I use CDs.
Step one: Use the CD as a painting palette.
When the palette becomes too full of paint, add a few Woodland Scenics tree bases and some gravel, sand, cat litter or similar.
Paint the whole thing with a suitable base colour, I use light brown from a crafts store. Flock to taste and add clump foliage, rocks or whatever. Now add the Woodland Scenics trees, but don't glue them, just slot them into their bases during games and pull them out afterwards, that way the CDs can be stored stacked and the loose trees chucked in a box.
As for the question of priming: acrylic paint sticks to CDs. It can be scraped off, but once covered in a base colour and a layer of glue for the flocking, it will not come off by accident.