Well, I have a 3 year old choc as you can see by my av.
He weighs 125lbs and I only feed him once a day at dinner time and he's not
over weight. Twice a day should be fine in moderation but don't over do it. As stated above they'll eat till they bloat themselfs.
Just spend as much time with them as you can training them and make it fun for them, its goes faster. And if they act like they get tired or bored of what their doing just stop. Go back and start again a little later. Remember the key is to try and make learning for the dog as fun as possible for them. Keep it fun and the longer they stay interested. And yes I did us a collar in the beginning and depending on how smart your dog is, it shouldn't take long. I had one that would also make noise when you used on em and after a couple times all I had to use was the noise button.