I will relate one "aha" moment I had a couple of years back, probably 3 years after Bob's Bump Camp, and thinking I had solved the weight forward problem by virtue of having attended the camp. In retrospect that thought was only in my head. I was in the bumps on Park City's Thaynes run when I REALLY tried driving my downhill shin into the boot tongue as I came around under the bump I had just turned around. I experienced a slowing of speed that I had never felt before in that situation. And up to then did not know that such slowing was even possible. It was as if that shin was pressing on an imaginary brake pedal- the more pressure on the boot tongue in a given turn, the more slowing. And the more control. It was a true revelation! I think that right up to that point I had not really taken the weight forward idea far enough- at that point in the turn my weight had always been too far aft. As we all know, weight on the tails at the end of the turn will cause the skis to scoot out from under you. I guess that over 25+ years of thinking I was skiing the bumps I had just assumed that that was how that point in a bump turn was supposed to feel- skis scooting out from under. The feeling of speed control was completely new. Even now, I only get that feeling about 8/10 bump turns at best, so there is still much improvement to be made.
There are many mantras to express the same end result of starting the turn with weight forward: "tips on the snow", "reverse bicycle pedal move", "dolphin turn". Perhaps the most useful visualization for me has been a variation on the dolphin turn/move. I try to imagine that as I tip the shovels of my skis into the trough at the beginning of the turn that I am trying to kick myself in the butt with my heel pieces. This takes quite a leap of faith the first couple of times because, at least for me, it feels like you are launching yourself into thin air. No visual grounding from seeing the tips of the skis or even the slope below. It can be very disconcerting. But I have found that's what it takes to get that damn weight far enough forward. So anyway, I think that despite a good start to the turn with the tips on the snow and engaging the trough between the bumps, I was still somehow managing to shift my weight back before getting into the belly of the turn described in the paragraph above. It's devilishly hard to put it all together, like Josh mentioned above.