Thats strange. Non metallic I can understand because the metal flake in the paint may scatter the signal to the LNB. But non gloss? If anything you would want gloss to let it self wash easier. Or snow/Ice to fall off. RF doesn't care about Gloss or flat. But
IF it did reflect more signal to the LNB that would be a good thing. Less rain fade.
Whats this brush stuff.??. One Spray can. Scuff it with a fine scotch pad , shot it, done and dry in 10min. If you need to match a color, go to your local Automotive paint supply and parts dealer. Carquest, NAPA etc. Or Sherwin Williams or Dupont auto paints store. The can computer match from a sample and put it in a 16oz spray can. From lacquer to Urethane to 2 coat. Urethane is nice.