A Couple More Questions of Muting The Bassnotes

My last post was on muting a walking bassline (see thread.) That's a bit hard for me to do right now. What this book I bought suggests is to go back to the beginning of it and try muting the bassline with the easier exercises. The bassline isn't moving in these exercises. I'm able to do this technique without much of a problem.

My question is this: when you are fingerpicking normally, you're forearm is resting on top of the guitar and you're hand hovers above the strings. Your fingertip is parallel to the string when you pick the note. To mute the bass strings you need to rest your hand on the bass strings near the bridge. This changes the posture and position of your hand and wrist. Your wrist is no longer in the neutral position it's extended and your fingers are flexed. When you pick the top strings your fingers are not parallel to them but sort of sideways. It's harder to get a clear sharp nice sound, i've found. What do i need to do to get a better sound? Also, I feel this position puts you at risk for injury. What can I do to lessen that?