scrape old waxoff your boards, and melt it down in an old beer can in a pot of boiling water. add something sticky to rejuvenate it. coconut oil is best. then let it cool and rip apart the beer can and youve got fine wax. thats what i do every now and then.
wax is wax, you might as well use the old stuff from your boards, you just need to make it sticky again or it will be like rubbing a candle on your board.