I usually do it one handed, grabbing the edges of the lenses with one hand, although I do the bridge thing too.
Really, though, if it starts slipping too much, I take a pair of needle nosed pliers and adjust those suckers, because they're not supposed to do that.
Really, though, if it starts slipping too much, I take a pair of needle nosed pliers and adjust those suckers, because they're not supposed to do that.