Originally Posted by spunkyruss
Some WD40 will help things along and allow the dislodged particles to stick to the rag for removal. Don't go crazy with the WD40, or you may thin the grease in your bottom bracket bearings.
TBH, I wouldn't stick WD40 down the seatpost at all, it's about 90% solvent with the tiniest bit of light oil thrown in. I don't why it gets so much mention as a lubricant, it's pretty pathetic even as a "jack of all trades".