I have done both. As significant as this problem is, I would suggest using the litter straight away. Most recently, we start with a completely clean litter box, brand new Clump and Seal litter and sprinkle the stuff on top and that works well for us. I know this next bit of information won't...
I have used Cat Attract when my cats have strayed form the litter box because I have not been a great kitty mom (too long between scoops) or my girl is recovering from a UTI. It has always worked well for us.
Please read those labels. Lots of fillers and preservatives, I'd like to eat french fries for every meal, but eventually, my doctor would have to get involved.