Dadfad,
1) You can apply oil washes using a paint brush. I personally prefer pointed brushes as they limit the area where oils are applied. Allow the tip to touch the panel line and the oil will creep by capillary action.
2) Oil washes go very well with acrylics.
3) Depending on the consistency of your wash, you can remove the excess by wiping it off with tissue or a soft cloth anywhere between 1 to 3 minutes after the oil wash is applied.
Hope this helps.