Variac Recommendation Needed

[MrMagnavox]

A friend of mine and I are beginning restoration on a 1952 Magnavox B&W television (i.e. new caps, resistors, tubes etc.). I've been advised many times to slowly "bring up the voltage" with a variac. I've never used a variac. What would be the best one to buy for this purpose? Where should I buy it? How much should I expect to spend? What voltage increase schedule should I use? Thanks much!