This is an important stage you are at considering the performance of the model.
First, sand the model well, all over then sand again! Everything you sand off now will be less mass you will have to support later while flying. This is more important for these smaller planes because of the limited area you have to work with. Be more aggressive on the solid parts and more so on the parts behind the CG.
Besides helping to lighten the frame a good sanding helps to prepare anything you put on top. Any and all prep work done before applying the first bit of paint is more important to the good looks of the finish in the long run.
When choosing colors, dark colors like black, brown, blue, green, orange and reds are heavier so try to use them only for accent trim.
Choose light colors like white, yellow, or cream for your base background color. Use enough to only get coverage! It is too easy to apply heavy coats trying to get good coverage adding unwanted weight. Weight that once added is difficult to remove.
Post pictures of before, during and after in the Half A forum!
Robert