just like almost everything, i put down a skim coat of gesso to start and worked from there. the wooden cradles paint different than canvas and if you use an ink on the cradle without gesso the ink will be absorbed by the wood.
as a point of interest- i only the gesso the actual front panel and not the sides. i like how if the ink or wet paint runs off the front panel that it is absorbed by the sides of the cradle.
on this bottom cradle i used a strip of painted paper and attached to the board after i had gotten my background done. and can you see i have had a circle obsession?....can't seem to help myself, but, i love them....