.....Paint a thin coat of epoxy over the area to be filled. Dry micro is then lumped over the area. The fill must be high, such that material is sanded away to bring the area into contour. The micro should be mixed very dry (lots of microspheres) to save weight. Let the micro cure at least 24 hours. Sand the micro overfill into contour using a hard sanding block, or spline with coarse (36 to 60-grit) sandpaper. Exercise extreme caution while sanding. A few careless strokes with coarse paper can ruin your structure!

STEP THREE: FEATHER FILL
..... Sand the surfaces lightly by hand or with a soft foam sanding block in preparation for feather fill. A spray or brush coat of feather fill will build up .02" to .03" thick, fill the glass weave and any medium sized out-of-contour spots. Feather fill will require several hours curing time before it can be sanded. The cured feather fill is sanded to contour using a spline or soft block and 100-grit sandpaper. Again, extreme caution must be exercised not to damage the glass structure in pursuit of a good finish. The contouring must stop immediately when the highest glass peaks begin to be visible as the feather fill is sanded away.
.....If you find that you have underestimated the fill required or just have a thin coat, don't hesitate to use a second coat of feather fill. A well prepared surface generally won't need more than one coat. When you have finished contouring the feather fill, the sur¬face should be basically smooth and fair. The primer to follow is not intended to be contoured heavily, just smoothed with finer sandpaper for a smooth finish while leaving a substantial ultra violet barrier.
.....After you have filled and contoured, reinspect for sanding damage; it is an easy thing to do! Remember, you are only allowed to sand into the first skin ply in local areas no greater than 2 inches in diameter and all of these areas must total less than 10% of the surface area. Wherever there is only one ply, or where the UNI cloth is crossed for strength (e.g. the canard and wing skins), no sanding of the ply is allowed, except for "scuffing Upll the surface. Be Careful!