Wax, nail polish or heat. All methods will work, some better than others.
I once had this discussion with a sage and worldly pipe master who gave me the pros and cons of each method and he stood by heating/extending/expanding. His process was all about control and patience: Gently heat (by candle, burnsamatic torch, lighter, or match) the business end of the tenon and once it's warm, use smaller sized drill bits to gradually extend/expand the circumference of the connection point. Gently, insert while warm, let it stretch to the circumference, then remove the bit. Don't wiggle or bend while inserted.
His advice...you can go up gradually in drill bits until you find the size you need, incrementally extending the circumference of the warm tenon, and if you work slowly and cautiously, it will gradually increase the circumference to fit the shank. Best to start small, run a test bit through the tenon and pick the next largest size, then and work your way up, checking to ensure you have not gone too large.
Drill bits? His answer: They are machined to a specific circumference...when inserted into the warm tenon, you should experience a uniform expansion. In addition they are also stamped with sizes, so you can work your way up incrementally and keep track of where you've been or where you need to go.
