Hey,
I went and bought a 2-stroke premix cup with graduations. I calculate how many OZ's to pour out of one container, and pour it into the premix cup. Then I pour in one full quart, let it sit for a few, hold the compression, turn over the motor by hand etc... Then after a few minutes, I pour in what's left in the second quart, minus what I calculated to pour out. Start it up, let it warm up, take a short ride around the 'hood (my neighbors love me!) then come back and check my oil. On my XR400, I could get it perfect on the dipstick, almost every time. However, on my new 650R, I tried it last weekend, and it came out low. I will double check my calculations, and try it again next time.
One other thing, make sure you folks check and clean your oil strainer screen regularly. Mine, on the low miles 650R I just bought, had debris and small metal slivers in it. Especially you guys with newer bikes, check that strainer screen. Don't be lazy because of a skidplate either. Good luck.