Of course, you can always serve from the mold. Much prettier on a plate tho. It depends on your mold, is it a metal ring? a sort'a bundt pan? or a glass dish.
Glass I would just serve it from the dish.
There are many ways to 'dump' your gel out. Try using a paper towel with a thin thin coat of oil has helped me without ruining anything.
The hot water trick is really in the timing and that is just experience. If it doesn't come out frst try, put it back in the fridge to firm up the area that DID loosen.
I grab my ring mold at opposite ends (say 3 and 9 o'clock - this might be dificult for people who've grown up with digital
) dunk in the hot water and jiggle/turn it slightly back and forth while counting to 15. Then out, plate on top, flip.
You could also add a bit more plain gelatin or lessen the water content a tad.