I've been repainting some doors and trim. The existing top layer of was not well adhere in some places and started to flake when sanding. So I have stripped the top layer, then sanded, but it seems like there are still slightly raised ridges (wood grain?) which is visible once I paint the satin top coat.
I'd been using a small sanding block, do I need a very large flat sanding tool? Do I need to fill these somehow? It would mean applying putty over a large area.