Soak them in a little water, just enough to cover the spikes for a few minutes. I replaced the spikes on my XPS-1s a about a month ago and it worked like a charm after wrestling with them dry at first. There was a lot of dirt and grit in there. Work the wrench back and forth a few times and they should pop out.
This works really well, just soaking them for a few minutes makes a big difference in loosening them. I changed some spikes the other day, right after I washed the shoes, they all came right out. Piece of cake.