Hi, I also got the molds done at my dentist.
I had one appointment to have the molds fitted (which was combined with my normal check up anyway) and then I just went and picked up the molds and bleach when it was ready.
I wore the molds on my teeth at night in bed. The first night they felt a bit weird but then I got used to it.
After one week my teeth were very white

and they were quite discoloured to begin with from drinking heaps of tea.
That was nearly 3 years ago and it is only now that I am thinking I'll order some more bleach for a touch up.
It cost me $450 for the molds and bleach. Money well spent as I was very happy.
I personally would not bother with the chemist type products. I tried a few and then realised that each time I wasted $50 on one I could just put the money towards the "real deal".
Go for it! You won't regret it