Those special snap-ring pliers with long thin tips do make removing the internal snap ring easier, but if you press and hold the piston down, there is plenty of working room to use a standard snap-ring pliers. I gently hold the master cylinder in my bench vice (using a towel to prevent damage) so that I can use one hand to press and hold the piston down, while using the other hand to remove the snap ring. Installation is even easier, once the snap-ring is started in the bore, I tap it down using a suitably sized deep socket, listening for the 'click' as it seats in the groove.
