Mutes are my favorite grabs by far. This is how I learned them.
First of all, don't worry about getting the big "X" cross in your skis until later on. If you spin left, what you want to focus on doing is bringing your left ski straight up by trying to touch your knee to your chest, THEN grab.
Once you are able to get your fingers on your ski, that's where they get fun. At this point you should be confident with holding it for a little bit long in the air so you can move on to tweaking the shit out of it. While keeping you lead arm nice and relaxed during the spin, just pull on the grab and force your boots together to get that classic mute look.
And in order to get that tweaked out Shredsauce style mute, imagine pulling the grab underneath you like you would if you were swinging a jump rope.