well, don't currently own anything 2 stroke, but, when I was doing the TCW3 in my cars tank, (1oz to 5 gal gas) I kept a couple little squeeze bottles with oz markings around (more recently bought some plastic screw top test tubes w/ ml markings) that i would pre dose. then it's just a mater of figuring where on the gas gauge it's about 5 gal from full... get to the pump, pour in the oz of oil, then fill up the tank.
for a gas can, same system. figure out how much you need for the desired ratio, pre dose the empty can, then fill it at the pump. the action of the fuel flowing into the tank should be enough to mix the oil sufficiently.
and there is no E0 gas around here. it's all min E10.
Casey's has E10, E15, and E85.
they used to have E0 91, but replaced it with E10 93 "Super Premium" and charge 5-10 Cents more for it than their "Premium" which is E10 91, which they charge the same as everyone else in the area does for "Premium" E10 93.
which really upset me. when they had the E0 that's what i got. my car got about 5 more MPG's with it, vs E10.