How do you handle white?
I use the Sennelier lights on top for highlights because they are soft and will sit on top of other colors. This is easier if you allow the OP painting to “set” overnight.
 If it's a large area, I will "reserve" it by putting down a white or light first (any brand). Because whatever color goes down first stains the paper. That way, if you put down a dark on top, you can scrape back to the light and then use a harder brand white to refine the area.

How do you blend OPs?
I blend my OPs with  a color blender tool, a paper towel, a rag or my finger. You could also use a tortillion.
I also like to blend using another color.
If I want to really spread it out like for an underpainting, I spread Weber's Res-N-Gel Quick Drying Extender Gel over it with a rag or paper towel.

How do you get details?
One way is to use Walnut Hollow oil pencils (found around here in the woodworking section of Michael’s craft store).
Another way is to put some oil pastel on the end of a color blender or tortillion.

Do Oil pastels ever dry? How do you frame it?
They do not dry and therefore do not crack like oil paint can. They do however, harden a bit over time. Since they do not dry, they must be protected when framed. The easiest way to protect an oil pastel painting is to frame it with glass and a mat. (The mat keeps the glass from touching the painting.) There are other ways to frame without glass but they are more involved. I'll go into them at a later date.