Hello,
Sanding sticks made for modeling seem expensive to me. The ones my wife uses for her fingernails seem to be the same thing (almost), but they are very coarse. I've come up with a way to buy cheap nail-file sticks and replace the sand paper.
In the photo below, working left to right, I start with the original nail-file. Then I peel off the 100 grit paper (2nd from left). 3rd from left shows the double-sided tape I've applied and trimmed. 4th stick shows where I've put 600 grit on half of the stick. The stick on the far right is 600 grit and 1200 grit. This entire process takes less than 5 minutes and when the abrasiveness on one of "my" sticks wears down, I just peal it off, reappl the double-sided tape and sandpaper of my choice.
