Wood – Dent in oak beam

After staining give a coat of clear finish, sanding it with a fine sandpaper (400G) to remove any raised grain or any dust that may have settled onto the drying finish. This will give you a good base to add your paint and the sanded surface will give it good adhesion. Steel wool has its purpose, but I would not use it here. That's only my opinion. My experience is the steel wool sheds metal bits everywhere, and may be a deal to clean up completely.

After the recommended dry time for the paint is over, give it your final clear coat. I know this did not answer your question about how long to wait before the top coat, but depending on what brand of paint you use, makes a difference. Each paint container always list how long it needs to dry before the next coat. Many usually only need 8 hours.

If you do not have that, the safe rule of thumb is, 24 hours if oil over oil, 2 days if water over oil. I don't know what to recommend if oil over water.

An easy way to test out stains is to apply an ample amount of the filler you are using to a scrap piece of wood. It is unlikely you will be able to match the wood. But judging by the amount of filler you have, I assume matching the filer is the biggest concern. Sand the filler on the chair and the scrap using the same tools( sandpaper etc ). Then test out the stains you pick on the scrap piece and hold it up to your chair. This way, you don't have to commit to a stain until you are fairly sure it will match.

Also, sometimes a paint supplier, Porter, Sherwin Williams, etc. has some professionals who actually still mix tints/stains. They can usually do a decent job of getting close to the stain match. Bring a good picture of the chair stain and the sample piece you made and they may be able to help. Otherwise, just get a bunch of small stain cans from your local big box and test away!

Happy hunting!!!