I think the main key is to add lots and lots of the flocking and when you think you have enough, add some more. then make sure you let it set for the full period they say before removing the excess. Remember, you can collect the excess that does not stick and reuse it again so it does not hurt anything to use a LOT when flocking. Ithe. Use a paint brush as suggested to help smooth it out and get out excess.
Interestingly enough, unlike Jim, the one time I didn’t have very good results and thought it was streaky and not very thick and looked bad was the time I used craft acrylic paint rather than the color adhesive you can get with the flocking. Was never really sure either why that was the case. I wondered if it was the paint, too thick of paint, not thick enough, Inconsistent on thickness, color I was using. It was the orange. What color were you using?