I previously wrote:

16 grit on a right angle sander.

Toller writes:

That sound like a good idea, and faster than setting up the dado set;
thanks.

Case you don't recognize it, right angle sander is the basic tool of the
fiberglass boat builder.

With some practice, you can almost become a sculpter, like the guys with
chain saws working in iceG.

BTW, 24 grit works better on a 4-1/2" sander.

Keep the 16 for the 9" unit.

Lew