My pup really responds well to correction. She's an incredibly easy dog. Normally a "ch" noise or "eh eh" or "leave it" works well. "eh eh" is her "stop that and pay attention" sound, as well as "nope, that's not quite right"... and it works really really well for her.
For yours, something to reinforce would probably be in order at this time, not to replace a "no", but just to reinforce it. Maybe a squirt bottle? Or the air spray thing. With the "no". And then phase it out as need be...