The paper bag trick is definitely a way of feeding I haven't tried but seems like it works quite well.

I'd imagine they'd eventually get it on their own soon enough. I've assist fed my hatchling about 4-5 times now and she still doesn't get the idea. Although she has been taking the assist feedings with more interest and a quicker bite down with each feeding, so hopefully she'll get the idea.

I assist her every 5 days with a F/T hopper and she seems to do just fine without over stressing. It's also a quick process so it doesn't seem like it puts too much stress on her.

Wish you luck with your hatchlings!