I don't know of any reliable way to fill the grooves so they totally don't show.
I would just go ahead and paint the paneling. I have seen it done and it looks nice. Sand it lightly and prime with Zinsser's Cover Stain (oil) and then paint with latex flat. The flat sheen will not reflect and makes the grooves less obvious.
BTW, shut off your caps lock; it is considered rude.