Wash the interior of the radio well before you dye it, so that all dust is removed. Allow the radio to dry for a day. When you wash the interior, use a slightly wet (rung out) rag--don't soak the interior, or else the glue joints will come loose.
T.
:The musical instrument parts and supply people: Stewart-McDonald sell a black stain for dying ebony fretboards I think would do well for the interior of your radio. Google: Stewart-McDonald. Be sure and try it on scrap first. Good luck.