Hi Loris,
It usually takes my prints about 45 minutes to develop. The print on unsized paper took well over 2 hours. The print sized with Gamblin took somewhere between 30-45 min. Anywhere up to an hour is fine with me. I'm using pretty cold water though, so I'm sure that lengthens the time.

I think I used somewhere around 1 or 1.5 teaspoons of the Gamblin mixture for a 8 in x 10 in print. Too much probably?