I can share my personal experience with having students mount and view cheek cells. I think the methylene blue is probably okay, but you can see cheek cells without stain. It's just harder to see them, they look like a box jellyfish. Gum chewing or recent meals make it more challenging as well. I think the gum removes most of the loose cheek cells.
Here's the procedure I had students follow with success:
1. Students use toothpicks to collect cells by scraping both inner cheeks for 15-30s.
2. Swipe the toothpick on clean slide.
3. Dry sample onto slide by waving in air or gently blowing (this is a crucial step).
4. Add stain (you may try without stain) and let sit for 30 sec
5. Gently rinse stain with eye dropper (carefully to prevent sample from washing off)
6. Add coverslip.
7. Using compound scope, start with lowest magnification and bring stage all the way up. You may also need to adjust light level at this point. When you have the slide in focus search for areas of dense cells. Cheek cells are very small at 40x magnification.
8. Center area of interest in the viewing field.
9. Go to higher magnification. and repeat to higher magnification
Another fun microscope sample is to look at local raw honey. Students can see the pollen from the plants the bees visited and make connections to ecology.
Any other suggestions from the community?