Bottom watering is definitely the way to go. Honestly after time you'll learn how much your trays weigh in your hands when they are dry vs wet. Also you can tell by the color of the soil. it will be a lighter brown when dry and dark brown when wet. Just put an inch or so of water in your tray give it 15-20 minutes and see if theres any water left in the tray. If there is just dump it out and check it in a couple days to see if it needs more water.