For applying oil I place 2 drops on the heel of my palm then smear it around between my hands and rub first one, then the other on the BACK of the strop.

For when:
I like to strop when the lather is soaking, but I also like to rub down a strop before I use it and this is best before a shower since the natural oils are still on my hands. I have found a compromise. I strop after I shower by having the wife rub down my strop or rubbing my hand on the back of her neck.