As for canned air, I couldn't be without my scuba diving cylinder !! Full bottle pressure is a little high at 3000psi but a regulator brings this down to around 30 and then a variable trigger allows fine adjustment. The best part is the air is very dry and highly purified, and it only costs £1.50 to fill ! This usually lasts for 2 - 6 months before refil.
I find the nose grease as mentioned above good for very fine scratches on the neg