I've Heard of Painting between the lines but, can this be done?

I sprayed a converter up inside as many voids as I could in the frame rails... I caught the run off the best I could and re applied it several times.... with out dipping the frame its the best I could do... I sprayed degreaser and rinced with water several times I used a garden sprayer that held a gallon and then with brake cleaner to get any residues then the treatment... I use the Eastwood products primers and then I use an epoxy enamel over everything when its done... then and undercoating.... but there is always some voids