Speed mods for homebuilts

Ok, say your building an Emeraude and your not looking to make it a
speed demon, you just want to close up a few gaps. As your building the
wings, you realize the sizable gaps at between the wing and the flaps,
& ailerons. What would anyone recommend to close these up while in the
building process instead of waiting until it's finished. Also what
other reccommondations would anyone have (besides building a different
plane) for plain old cleaing up the efficiency of the plane? Not
wanting to change the design, just want to build it in instead of
adding after market product.
Lou