i've only used the spray for for tong feeding, but i ended up stopping and using zoo med calcium powder. the spray really stuck to the food quite well and made a shellac-like coating over it. i felt like it was good for pre-killed food like pinkies and such, but not so great for live crickets and worms. though, the more i think about it, it would probably be great to use on earthworms because they're so slimy and rub the calcium powder off quite easily.

all in all i think tong feeding really is the best thing to do because it prevents a lot of substrate ingestion but this, of course, is your own decision. i've had some trouble tong feeding my babies, they seem afraid of them, hahaha.