I ended up using toothpicks after all. I found that if I just gently push them through into the foam core they didn't break after all. Why I thought using a hammer was necessary I don't know; that just shattered them. I was able to get the splinter out of my finger eventually and the blood doesn't show up in the photo. Anywho, the swatch blocked nicely and is now ready to go.
Weave as you go, weave as you go... why can't I get that through my head? I spent two hours yesterday just weaving in ends on the swatches and I only managed to get half of them finished. Once I get the other half woven I can get them tagged and start answering questions. This HAS to be shipped Monday to meet the deadline! Oh the pressure....