I have an oak plywood window seat that I want to paint. It was poly’d years ago and pet use has worn the wood down in the grain areas throughout the surface. I want to fill it smooth and sand before I paint.

How should I prep this wood so that the wood filler is sure to stay adhered to it?

The research I have done suggests tsp comes after wood fill. I also think I need to rough up the remaining poly first. Should I sand lightly to create an abrasive surface, then tsp, then fill, sand, tsp again?

I will probably use a leftover squeeze tube of wood filler because it’s easy to use. The paint will be thick latex (ben moore regal semigloss).

Pet use will be prohibited on the painted area. After paint cures (30 days), I may lay some temporary mats (as underlayment) and 18” tiles on the surface for the pets, with a lattice border to contain the loose tiles tightly. (I can always repaint the seat if the painted surface is marred. I don’t want the tile to be permanent.) If you have a suggestion as to how I should protect the painted surface, let me know. Right now I’m thinking about using an old sticky yoga mat, but it might be a good idea to have some kind of liner underneath. All of my other windows and woodwork are painted with the BM regal semigloss, so I don’t want to do a different permanent treatment on this window.

Thanks for any help!