Ummm, mixing it wrong? There is nothing to mix, just dump it into the bin with the insects.
Actually my Dubia roaches can smell the stuff when I open the bag and come running out from under the egg crating in their tanks. It's like crack to them!:yikes::yahoo:
As for crickets. Lay your paper towel tubes down and then stack your egg crate, etc., up in the tank or tub. Place any food up near the top. Especially the gut load powder. I place a flat piece of cardboard on top of the egg crate and then dump the powder on top of that.
It's not that they don't like it. It's just not where they expect it to be. If you put the powder, or most foods on the bottom, the crickets will ignore it and defecate on it.
I read a report that sited white potatoes as possibly leaching calcium out of feeder insects, so I remove this from them if the supplier used white spuds to hydrate the crickets in shipping. (I throw the spuds into the super worm bin.)
If you have too much veggie content in the tubs, the crickets will not eat as much gut load and the tub will have a very high moisture level from them defecating all the extra fluids which is deadly to holding crickets for any period of time.

If your egg crate is moist or soggy, back off of the veggies or hydration gel.
I also place spot lights above, or pointed at their bins. Not too hot, just enough to stimulate them to eat, chirp and be happy.:banana:
I hope that helps,
Michael