Please give me your ideas

[ChadHadsell]

Shellac will cover and seal anything. Once you clean it, I'd definitely go with shellac as a "primer" just in case any oil or cleaner remains. (If you use de-waxed shellac, so you can then go over it with your choice of finish. Every finish will stick to de-waxed shellac.)

If you're concerned about the look, and the various cleaning methods don't seem to work well enough, then you could use a stain or dye over the first coat of shellac to even out the color.

[oldiron]

placing the board(oil stain side down)on absorbent will surely help with some of the oil removal. I would NOT pressure wash the board!It will surely raise the grain and could very possibly warp the board which will create even more problems.

Mike