If you take a peak at an earlier post, where I start me seeds in soil, Seed Starter Trays, in the image of the shelf, and trays, you can see an LED light above, then the tray, then at left of each tray a black wire left bottom. That goes to a thin black heat mat, under each seed tray. I kept the heat mats on, and entire shelf covered in plastic sheeting, to help retain heat and moisture for my basement seed starting.

For the Papertowel method, since the squash and pumpkin, etc all have lower germination rates (maybe 1 of 2? or 2 of 5 seeds germinate?) I can see which seeds will germinate before taking up space in soil Seed Starter Trays.

Not sure if you saw, but there's some 200 plus seedlings going on (tomato, pepper, zucchini, cucumber, squash, brussels sprouts, tons of herbs and more)... so, each seed cell is prime real estate!