You can put paste on the left over fabric strop. Either diamond spray or CrOx will work well on there, just dont put too much on. A little goes a long way!

In terms of which paste to use, both work well. I find the diamond spray leaves the edge a little harsher than CrOx, but using it on a fabric helps reduce this. Its really up to you which one you use, they are both good IMHO. I've not noticed any difference in sharpness though.