Adding silica as SJ34 suggests is the ticket. The silica will add non sag/run properties to the epoxy bog. We will blend i part silica to 3 parts micro ballons to have non sag and easier sanding. Careful application will minimize the sanding required. It would be unlikely to get a fair surface with only one application of bog. Add bog sand and then add more bog to the low areas. Repeat as necessary to achieve the desired surface.