Apologies if this question has already been ask, I couldn't seem to find a thread on this topic. I own a set of 4x4 filters, a variety of glass Tiffen FX and ND filters. I just haven't found a way of cleaning them without smearing the filter. I've tried a variety of methods, including rosco fluid/tissue, pancro, some other brand of spray on lens fluid I have in my kit; I haven't found a way that works yet.
What is the best way you have found to clean filters? Circular cleaning from the centre like a lens, or just go crazy?
Any specific fluid/tissue brand combination that seems to work best?
Also a fun story for everyone. I was prepping kit for a shoot at a rental house the other week, and the filters had all been repackaged in the plastic like most rental houses do. The word 'OK' (after being cleaned by the rental house) was written onto the plastic for each filter with permanent marker, which had gone through onto every filter!