Flocking

Rather than flocking, I prefer to use embossing powder. I think it gives a more realistic scale texture and it is easy to apply. Just paint a coat of clear (I use Future) where you want the "flocking" sprinkle the embossing powder over the area and shake it about to get good coverage. You can collect the excess for reuse. Once the clear has set up, check for gaps which may require an additional application, then you just gently paint the powder the color you want it to be which also helps to further secure the powder. Assuming 1/24 - 1/25 scale If you are using Bare Metal Foil or similar, I agree that it is probably best to foil first.

x2, and you won't damage the flocking while trying to put the metal on and get it burnished down.

Do the metal first. That way you wont be trying to lay metal over the flocking.( the metal wont lay flat with bits of debries under it.) Then mask the metal, then flock.