I've been experimenting with placing seeds directly in hydroton with a bubbler below the 3 inch net pot bottoms and so far every single seed has germinated within 3 days... no need for paper towel, no need for rockwool... just put seeds in below one layer of hydroton and believe me, it'll have plenty of support as the taproot works it's way through all the bends and turns it needs to make in order to find the water below.

The bubbles pop and pretty much soak the bottom 2/3rds of the hydroton and if you cover the top with one of those premade foam black inserts it keeps hydroton moist all the way to the top... perfect conditions to germinate... no extra warming pads needed either for some reason. I couldn't believe every one has popped. It may help to make sure seeds first sink in a small container of water but I bet even that is not needed.

this method really works. better than having your rockwool over soak.... just let all that moist air do the trick...peace to all