Just finished sleeving all* of my Dominion cards.
Since I got the 3 promos from boardgamegeek -- most importantly Black Market and Stash -- I had to think a bit about how to "sort" things.
So this is what I ended up with:
1) Put all of the blue-backed "placeholders" aside; don't sleeve them, don't use them.
2) Create a new "randomizer deck" out of 1 of each of the regular-backed cards, to be used instead of the Android program I've been using ...
3) .... except use a blank, with "STASH" written in sharpie, instead of the differently-backed Stash, for total purity in randomization. This is the one case where I'll have to go digging into the box if a card is bought from black market, but I think it's the lessest evil.
I might backpedal on 3, and replace it with an actual copy of Stash, and no tears will be shed about the sharpie marks anyway... but I'll see how it goes for now. It only matters in the case of:
* Black Market in the Supply
* Stash not in the Supply
* Drawing Stash as one of the Black Market choices.
which is a pretty rare event, mathematically speaking anyway.
And my ultimate plan is to eventually put all the cards into a box tall enough to stand up a card vertically (such as the original box with some dividers shoved in), and use the blue-backed cards as dividers.