Digital BW, The Print

So far I have been purchasing individual K7 cartridges for my R2400. I 
have noticed that there is a fair amount of ink remaining when the 
printer utility says the cartridge is empty, apparently due to ink 
capacity differences between Epson and Piezo cartridges. I have been 
thinking of re-using cartridges and purchasing ink by the bottle. Can 
anyone tell me how to refill cartridgres safely and if a chip re-setter 
is required for the R2400? If so, where can I get one? Also, will 
refilling for a long period of time end up in residue building up 
within the cartridge?

I am also interested in this method for creating cleaning cartridges 
for my R2400 which seems to clog if I don't use it every week. It is 
very dry here, so perhaps a humidifier in my office might help. Any 
information or links to sites with instructions or cleaning cartridges 
compatible with Piezo K7 inks would be appreciated.

Thank you.

Paul