I pour all the sizes with the bigger WB800 wires and do sometimes have to trim them to fit some of the smaller mold cavities. I keep a pair of heavy cutters on my bench just for that purpose. I'll occasionally get one that pokes through the side of a head, but not often. I had too many problems with the smaller wires getting loose in the heads, so went to only using the bigger wire keeper.
Drop Out is a dry graphite type spray that is used for pouring bullet molds. It creates a thin coating so the lead comes out of the mold easier and it can also help with flow when pouring. Any type of dry graphite spray will do the same thing, but the Drop Out brand is often mentioned because it is sold specifically for pouring, and it does stay on the surface of the mold cavity a good long time.