Flashing rhymes with:
clashing, lashing, slashing, splashing, bashing, caching, cashing, clashing, crashing, dashing, fasching, gnashing, hashing, lashing, rehashing, slashing, smashing, splashing, stashing, thrashing, trashing
Flashing sounds like:
falcons, feliciano's, felkins, filkins, flagging, flaking, flashguns, fleecing, flexing, flicking, flocking, flogging, flushing, foolishness, fulgencio