A lot of good advice here. When applying the tissue, you want to glue it down ONLY around the outside edges until it is dry. For example, when doing a wing, dope the tissue down only on the LE, TE, and inboard and outboard ribs, not the ones in the middle. I prefer to let the water dry on the tissue first, then seal with dope. When you apply the sealing coats, the tissue should adhere to the center structure then.
Also, on a FF model, I would use colored dope sparingly, it is heavier than clear and a bit of weight makes a big difference on the small FF models.
FWIW, I still haven't been able to get as nice a covering job with plastic film as I could with dope and tissue. Guess I need more practice !