Try lifting one finger after movement starts, then other finger when correct value/position. Will continue as a 2-finger entry so long as it began as such. Works on my iPhone anyway.
[Update] Fingers needn't be placed together, if that helps. You can select/hold control finger, then simply ensure another finger touches screen elsewhere before movement. Once movement, either finger may be lifted. With a little practice, easy enough to avoid cluttered areas. Focus on placing second finger in blank area, then lifting first finger early if that's in congestion. It's such a flexible system, the first finger doesn't even need to be the one on the control. You'll get it.