Never harvested directly from a conical before (don't own one..) but you may just need to wash what you pulled out. It is very likely that along with the trub that you are getting out the bottom, yeast is also there. After pulling off the bottom once or twice, collect some in a large, sanitized jar and allow it to settle for a bit. You can then decant the top layer of yeast off of the settled trub at the bottom. This should allow you to harvest the yeast, regardless of whether trub came along with it or not.