I am trying to repair/do-it-right a staircase hand rail that I removed the varnish from while trying to remove crayon.... It was obviously a thin coat originally. I want a clear, non-yellowing finish and I have found that catalyzed varnish or 2k conversion varnish is the way to obtain a clear finish. But, the descriptions I've seen all say 'spray only'. I want to wipe it on and do not see why I can't. Any information on why spraying is the only method would be appreciated.