I have used the method described by Jules many times, have tied cot ten balls to baler twine or even just a piece of tissue paper, it has always worked.  Dave NV is right about the wire lubricant, some GB lubricant has really helped when pulling lots of wires through a small conduit. 

One thing, make sure there is nothing in the plastic pipe before you vacuum the twine through the hole.  I used some used oilfield plastic flow pipe once, when I sucked the "pig" of cot ten through the pipe, I filled my Mother-in-laws Filter Queen vacuum cleaner with used oil.  We thought we had cleaned and drained it before we buried it in the ground.  Thankfully, she was a great and understanding MIL, but I worked very hard to get all that used crude oil out of her best vacuum cleaner before returning it back to her.