as jan said, try to keep your shuffle at it's location. to do a 42* you don't have to move your shuffle right or left.
also when getting back into the shuffle it really helped me to "unfeed" the 2d sun; i throw up the diabolo you would usually throw up after the 2d sun when doing a fts 2-1 or 42*s just a bit, wich gives the other two diabolos a bit more time to get in the 3d shuffle.