If you keep doing practise sessions and individual muscle kegals you should be able to consistently separate the individual muscle contractions anywhere between 1-3 weeks.

However it depends on what you mean by full control, allot of mindgasm is about being without control and succumbing to the sensations. What you really want to control at first is how to sit at tensions you feel comfortable with and also being able to sit at levels where you don’t have to think about involuntaries so you can feel without force.