After you have shaped the tip and sanded to make it smooth simply saturate the side of the tip with super glue being careful not to get glue on the surface of the tip or on the ferrule. Have been doing this with all my tips for the last 20 years and have had no problems with mushrooming since.
I learned that trick about 20 years ago from Jon Z. at Red Shoes and Jerimy Chambers. Whenever they put a new tip on for me, they would super glue the edges and then burnish. I have NEVER had a tip mushroom. Any new cue that I get, the super glue treatment is done right away.