My Pac is *slowly* learning to tong feed, but doesn't always feed from the tongs. When he shys away from the tongs I use some playing cards as "plates".

Basically, I had a brand new box of playing cards that I never used. I take a card out and wash it thoroughly with warm dechlorinated water, dry it off, then set it in front of him at feeding time. I then place a dusted nightcrawler piece on the card and once it wiggles a couple times he snatches it off the card.

I do this for a couple reasons - to prevent the dusted worm from picking up pieces of substrate and to prevent the worm from making a mess in the terrarium.

Once I'm done feeding him I take the card out and wash it thoroughly again (to remove all the yucky, slimy worm gunk) and reuse it the next day or next feeding.

It works pretty good in my situation. If your frog lurches at any little movement in front of it this may not be a great solution because it will probably go after you and the card when you set it in. If you have a more cautious frog like mine it might work well.

The only issue I've ever had doing this is one time Orion lunged forward and stepped on the edge of the card flipping the card over and dumping worm parts on his head. It was like something from The Three Stooges. Quite comical

Maybe you could try something like this to feed your Pac worms without the worry of it accidentally gulping some substrate.