I tried various things, but there's this desert sand stuff that worked really well. Plain kitty litter was terrible, since dogs pee more than cats, it basically turns to mud. Wood shavings work well too, but you end up having to dump the whole thing instead of just scooping.
This stuff is what worked best:
Since Tango was so small I used an extra large cat box, but I know they make dog-sized litter boxes too.