I think rigging tape (aka 3M vinyl electric tape from Home Depot) might be your best bet for helping the knots over the rigging; if you wrap the knots so there's a taper on each side. Worth a try anyway.

Also -- if you spray the tapered taped area with McLube Sailkote the surface of the tape will be more slippery and less likely to grab. BTW I use McLube on wires before pulling, and it makes a big difference.