Jim with pieces like that, I use my cleaning solution. fairly simple: 1/3we equal parts , turpintine , denatured alcohol, BLO. Use a very fine steal wool or burlap but something wit a little tooth to it, work an area 2x3". you will feel the top finish losen up which will take the dirt off and remove scratches. do the next area and so on. Finish one direction. Wipe the excess off with a clean rag. About 6-8 hours there will be a film over the piece. Buff this off with a clean rag. It will buff out much like a wax. What I do when I first start a cleaning is work an obscure area of the piece to see how much pressure I need to put on the cleaning pad and how long I need to work an area before the finish lossens.
I dream a lot. I do more painting when I'm not painting. It's in the subconscious.
::: Andrew Wyeth :::