Hey Tom
I take it the SG is the thicker Green cap ?
Myself , I prefer the blue cap SG....Kinda confused on which one you were talking about ? Several types , and I think some are brush on ..some are thicker gel =Gorilla green cap. I get along fine with the nozzle head that comes with the bottle. Just enough to WET the quill lightly. I kinda move along quickly zigzagging;)
I just don't like the gel. Never tried a brush or switching the bottle. IF you could get that system with a bottle/mini brush like women use for nails I would think it would be good ., but likely the brush would soil well before getting through several arrows ?
I did a few wood arrows a year or so back and finished them with waterbased polycrilic as well...The Gorilla held just fine for me on the wood shafts without wraps...so You are likely good to go.
That Gorilla blue is GOOD STUFF