Fuel/oil mix

[fetoma]

My 86' 140VR has the oiler system removed, so I have to mix. What are you guys doing with:

*Ratio?- I've read 50:1- what ratio do you use?
*When to add? Do you fill up after your day on the way home and add the oil then, or do you fill up before you go out and then add the oil. My concern is how well will the oil mix dilute with the gas as to not hurt the engine.
*What oil is good quality?

Thanks,
Frank