Watch the Muting Techniques online guitar lesson by Jasper Mortier from 50 Blues Bass Licks You Must Know
If you want to be able to control the length of the notes being played, you first should be able to let them ring as long as possible. Try to do the next exercise without muting a note, before you move on to the next note. Do this without tension in your hands. And if it's hard: slow down! If it takes musclepower to achieve a certain position you're doing something wrong. Don’t stress the fingers, try to do it as relaxed as possible. These kind of topics can be easily over-analyzed. This can interfere with your playing, because your too focused on the details. So my advise: after you’ve fooled around with it for a while, let it go! Don’t let it interfere with the fun of playing. If you pay attention to it every now and then you will slowly integrate it in your playing. After a while you will surprise yourself: suddenly you’ll be doing it automatically. It became a part of your natural way of playing. And you'll probably develop some techniques of your own too! On the amplified upright muting non used strings is extra important, because they have the tendency to start feeding back. Sometimes I'm even using my chin to mute the E-string for instance: whatever it takes people!