I regularly play with two guys who only hit slice from both sides (well one guy can hit topspin FHs but is loath to do so). The trick with both these guys is to NOT hit balls that bounce up, such as balls with lots of top, particularly to the FH side because that makes hitting the slice much easier for them. (On the BH side it is easier to slice off a low ball.) If I keep the ball low to their FH, I see a lot more errors and soft balls.
One more note: you have to be careful with your volleys because they leave your racquet at a lower angle than you expect.