I was trying to think of how I was going to shape 2mm wide x 1mm thick balsa strips into 'D' mouldings for my ST wheelhouse side reinforcements, without sanding and probably breaking them. I came up with this simple method which can be done on or off the model. I had already glued the strips on but it still worked well like that. I used a piece of ply scrap to make a simple tool with the required shape filed into it at about 45 deg, and the end radiused to run on the board/model. There is only enough shape to make the moulding, with the radius touching the board as support (and a sort of stop) see drawing.
The photos show the tool (top R) and the top moulding done (bit hard to see but you can see the square side has gone) All you do is rub the tool along the moulding to shape it, and it can be coated with thin cyno to stop it returning slightly to original shape.