While I'm sure this isn't the answer you're looking for, my answer is simple: don't use a card shuffler.
In my experience, card shufflers tend to shred whatever cards they're used to shuffle over the course of far too few (not more than a couple dozen) shuffles - I watched several early Magic players ruin cards on them, and Magic cards are actually substantially sturdier than many other games' cards. Casinos can generally get away with using automatic shufflers (and note that the shufflers casinos have access to are much higher-quality than anything you're likely to find at any reasonable price) because they have little need for a deck of cards to last more than a couple of hours, but I'd strongly disrecommend them for any game you want to play for more than a handful of sessions.