I don't know how thick your copper is
on the boards so I won't suggest scubbing
them with a scotch-brite. However, I can offer
a means of making a fine mat surface on the copper.
Any book on electroplating, can show formulae for
a simple copper sulfate / acid bath for electoplating or
electroforming. By placing your plate in this bath
with another plate of copper as a cathode or as
an anode you can produce this surface in minutes.
Power in the form of DC can come from a car battery.
Be careful ! Actually, all the power you would need
for this could come from a 6v lantern battery.
good luck,
Phillip Murphy