Traditional Friction Tuners

 All you traditional dulcimer builders who use friction tuners. What is the best way to tune and tighten the pegs to where they are not slipping ? I have 2 dulcimers one is a courting dulcimer it has 8 the other has 4. On the courting dulcimer by the time I get one side tuned the other side has slipped. I have peg drops and I have used water. What do you recommend for the ones you build?