In an official match or any match that uses ITTF rules. ITTF approved and current listed racket covering most be used on the blade.
If only one side will be used, then the other side must be painted the opposite colour of red/black.
In the cast of the player using wood (painted or not) to contact the ball purposely, then it is illegal based on ITTF rules.
The contact has to be on a ITTF approved rubber basically.
Regarding training, it is popular to train juniors with one side wood and one side rubbers - whereby the coach can twiddle.
This is to let the junior get used to different kind of spins, and controling incoming spin or anti spin (wood) for that matter
Playing with wood does not necessary crack balls faster too, unless they are not training and wacking the ball on purpose