A glossy base coat is a must!
The semi-gloss area you are referring to is particle build up of dried Future.
Trying to remove wash from this area is near impossible as you have found.
The smoother the base coat the easier it will be to get a nice even wash into the panel lines, and to remove the excess without disturbing the areas you want accented.
Just remeber to apply your Future so it looks wet and has no runs.
If you have over spray or rough areas, apply a little more Future as it will 'meld' with these areas.
Takes some practice, but is well worth the effort.
Hope this helps