First, all washes work best on a gloss surface. I paint mostly with enamels, then gloss with Future, then apply an oil wash. Regarding your questions:
1. Really Depends on the base colors your putting the wash over, but the ones I find most useful are Burnt Umber, Raw Umber, Burnt Sienna, Raw Sienna, Paynes Gray, Ivory Black & Yellow Ochre. Of these, the ones I use most in my work are Burnt Umber & Paynes Gray.
2. I use either Mineral Spirits or Turpenoid.
3. Same as #2, although Lacquer Thinner works well but is hard on the brushes.
4. A lot longer than Acrylics. Allow at least 24 hours dry time for an oil wash.
5. You can go straight to a flat coat, once the oil wash has cured.
Regards, Rick
RICK
At My Age, I've Seen It All, Done It All, But I Don't Remember It All...