Anybody ever cross breed before?

I'm going to attempt to cross Thai with White Widow. I am flowering my male Thai plant separately so I don't pollinate my other females, but when is the best time to pollinate the one White Widow plant? I was going to pollinate just one branch, but at how many weeks should I do this and how much time do the seeds need to fully grow and mature? Also, should I harvest at the same time I would normally? Any info would be great.

i say pollinate 5 weeks before u harvest and remember one cola could have as much as 50 to 100 seeds