The best method for pushing in a speaker cone, is to not push it in. People do this all the time to 'feel for coil rub'. Well, if you cant guarantee you are pushing the coil exactly straight down, and you cant, then you cant be sure any coil rub you feel (or dont feel) is not simply due to your improper pressure. About the only thing pushing the cone in is good for is to simply see if the motor is actually locked up, which is fairly rare anyway.