:These are trim pieces, 3/4"-1"
: thick. I know a contractor that does vinyl siding. He was taking the cedar
: he pulled off of houses to the composting yard to be ground up.

I'd rip the boards as they are into 1/4 inch (or thinner strips).

Then, rather than work on removing the paint, I'd remove the wood the paint is resting on by putting bead and cove edges on the strips. Bead the painted side. If there is a slight residue of paint remaning on the top of the bead this will be buried inside the matching cove and not be seen, and should not affect gluing strength.

hope this helps

PGJ