There really is no formula for speeding things up. And doing the down motion definitely takes longer for almost everyone. My PT said it was because of the muscles involved in that motion.
What I did as far as stairs, was to try doing a couple steps (fairly) normally each day. So basically go down stairs one foot at a time, but for the last one or two try it normally. Gradually it got a bit easier and I'd do a couple more.
At 12 weeks, I could pretty well (though not totally comfortably) do the down steps (with the railing) but I didn't do them more than once per day that way.