A Spratts comb with an elastic band threaded through the teeth seems to work quite well although you have to be careful to comb the same way that the seed is lying otherwise it could be pushed further in.
Chaz's last encounter with these little horrors needed a couple of hours of careful combing and use of tweezers to get them all out, especially those that had lodged in the skin around the armpits, underneath his collar and between his paw pads.
Bob.