I have a few hairbrushes I got at Kmart when they were in business like 12 years ago. The brushes were actually in the kids section and have little rubber balls on top of each stem. They bristles also have a lot of give to them. They are also on the smaller side, coming from the kids section. I think the key was they are flexible, soft and have rubber tipped bristles. The choice of brush is important.
Also worth mentioning is if you're tickle torturing a lees feet with a brush, the feet should be bare. Add a little baby oil and then the brush slides around nicely. Mix up different pressures and different strokes as you go along. Feet should be bare for the BEST effect.
When I use the brush, the lee is locked in full leather restraints and usually strapped down to a table with multiple straps on the legs and ankles. Feet are bare.