Smaller bonsai may be soaked for a few minutes up to the depth of the bonsai containers' rim. For larger trees in which soaking is impractical, the tree should be watered a few times in succession to insure that the entire volume of the pot is saturated and water flows freely from the drainage holes.

We like to water our trees at least twice in succession about five minutes apart. The first watering will wet the soil mix and allow it to accept additional moisture in the subsequent pass. If the soil surface is covered with moss, it may be necessary to douse the tree several times to ensure that the water is actually penetrating the surface. In hot weather, it's a good idea to water the pots as well as the trees to cool them
Watering the foliage of plants cleans away pollutants.

Because I live in Michigan, it's impractical to be able to keep my Bonsai tree outside during this season. I've been keeping it in the window with a tiny aquarium heating pad underneath the drainage catching pan to ensure that it doesn't get too cold. I keep a light on it (about 12" away from the pot itself) for about 12 hours a day, and water it when I check the moisture of the soil and it doesn't feel "wet" enough, per se. Am I doing all of this correctly?

For the smaller trees would you do the watering once or a couple of times like you would with a bigger tree?

Also for the bigger trees how much water do you put on it for each watering?

Hello,
Immersing the pot is perfectly acceptable, the water should cover the soil line. But, be sure not to over water your tree. Use a toothpick or a chop stick and stick it into the soil, if the pick or stick come out with soil on them, it's not time to water. If they are clean, time to water.
Another way to water is to use a watering can with a rosette but, the immersion method is by far the best method as far as I am concerned.
I like both methods actually. I usually water from above (cleans foliage and pulls gases down through the soil profile) but once a week or two (this time of year its weekly) I do it by immersion (I moss the tops of most of my pots so the depth is irrelevant). The only reason to not go past the edge of the pot is to keep lighter soil components from floating...

Thanks...!

Hi Kilojim:)

As u asked with watering Small/Large Bonsai's, it's best just to giver the smaller Bonsai's just one water per time. But with the bigger Trees it's better to do a few water's within 5-10 mins apart from each other, That way the water that didn't get to the root's the 1st time will be able to sink into the soil:)

Cheer's Jb