Digital BW, The Print

I just ordered the equipment to refill cartridges with Ultra Tone 
ink.  My question concerns cartridges without the poppet vales (the 
ones I bought).  Once you bottom fill one chamber and move to the 
next one how do keep the ink from dripping out?  Do you put pieces of 
electrical tape over the vent hole?  Are empty cartridges with poppet 
valves available anywhere?

Thanks,

Tom Husband