As well as the tips above I find that my youngest brushes really well when he "copies Mummy". If he is in the bath I give him his brush (cos this is messy) and kneel down beside him and brush my teeth... he copies me. If I do down one side he does the same... if I do my tongue he does it too. This has been the best way at getting him to focus on doing his whole mouth... otherwise he just tends to do his front top teeth. Oh and he can only spit when Mummy spits because otherwise he will spit the toothpaste out before he has brushed it properly and wastes it.... same with rinsing.