Recently picked up 12 gal. Due to duration of stay(30 days). Which is the better way to fly? Run directly to wagon or black holding then to wagon? 20 gal black. Is there a rule of thumb on how long one should let black contents brew(urine only). As it is quite a while to fill holding tank. I use a fomaldihide free deorderizer in black tank and have not detected any oder after 11 days.