Setting your wheel and foams up first makes a big difference too I think. You can use the foam to balance the wheel to a large degree.

Last night I set the wheel and foam on the balancer, found the heavy point and then turned the foam through 180 degrees on the rim and it balanced the wheel and foam.

Obviously this leaves the tyre which could be out of balance, but less weight required to balance just the trye, rather than wheel, foam and tyre.

Mark the wheel and foam and ensure that when you put it all together the marks line up.