That's a new one for me. I hurl realistic nymphs and get snubbed and they chuck glued on coffee beans, it ain't fair.
I have found that just a little puff or glob of white can often get a strike, especially in moving water. They seem to snatch up bits and test them for suitablity as food.
One technique that I tried for a few days this summer was tossing corn into the current above feeding carp until they got chummed up then chuck and duck a foam corn fly at them with a small split shot a foot above. They actually fought over the fly and would rise to take them out of anywhere in the water column.
It got too easy after a while but it was good fun for a while.