Actually that was one of my biggest problems with aspen, I had a few snakes get a mouth full when trying to strike their prey. I switched over to Reptichip and never had that happen again, it's a coconut husk substrate that comes in a block that expands when wet. Because of that I would never go back to aspen.

Personally I would never try to force feed a snake anything, especially using tongs. It can be a traumatic experience for the snake, especially if you don't do it right, and that alone can make them go off of food.

I've also never had luck just leaving a dead rodent in the cage with my ball pythons, I usually use tongs and just hang it in front of the snake for about 30 seconds. If he doesn't eat I'll try again in a day or two with small snakes, or for bigger snakes try the next week. I feed my hatchlings twice a week and my larger snakes once a week.