I've found that if I use my B string to anchor my right hand it gives me a good position to mute strings and the B is already muted by my thumb.I used to anchor my thumb on the neck pickup of my Jazzes or my Peavey but found it wasn't too much of a change just to move my thumb to the B string.
Also to the original poster,a good way to get used to a fiver is to learn all your new material on it instead of a four.It's good to try and play all the old songs you already know on your 4 string on your five and try different positions but when you memorize the tunes on a fiver it opens up new ways to play.Songs in E you can play staight accross the board in the fifth position and songs in D and C give you a new lower root if you want.All the material in the band I've been in for four years I've learned on fivers and now it's hard to play some of them on a four,I've got to stop and think about how to play it.
Also to the original poster,a good way to get used to a fiver is to learn all your new material on it instead of a four.It's good to try and play all the old songs you already know on your 4 string on your five and try different positions but when you memorize the tunes on a fiver it opens up new ways to play.Songs in E you can play staight accross the board in the fifth position and songs in D and C give you a new lower root if you want.All the material in the band I've been in for four years I've learned on fivers and now it's hard to play some of them on a four,I've got to stop and think about how to play it.