Can pore filler still be used atop three coats of finish on oak?
Greg Williams: If the coats are quite thin, maybe. If thick, I wouldn’t try it. I would do a small test patch to determine that the filler would sufficiently adhere within the pores to allow me to level it without pulling it out.
Tim Inman: If the pores of the wood are still “open” and receptive to the filler, it will work. If they are closed or partially filled with finish (which they almost certainly would be after three good coats of finish,) you’ll have trouble.
Michael Dresdner: To take it a step further, oil-based filler is more likely to pull back out of pores partially sealed with finish. Thus, your best bet when filling over finish is to use waterbased pore filler.