I found a pack of brushes in the kids craft section of IKEA for like $3.00, and seriously, they are AMAZING brushes for that price. I got them to use for actual painting, but I did pull one out to use as a glue brush and it's so awesome. Love it. I like using a brush with finer bristles because you can paint glue on with the detail you need for the small, detailed surfaces on a violin.
Here's a recent painting I did, just for jollies. Painting, lutherie, writing—it all comes from the same creative center. I consider myself an artist with four hats under the artist umbrella: painter, performer, luthier, writer.