Topic: $3.00 filter
I used these plumbing filters for 5 years and pounds and pounds of filament going through 0.5mm nozzle without any problems at all.
Unless you are using 0.2mm nozzle for printing, you can double those filters and place them inside the barrel and turn them 45 degree apart from each other, effectively doubling their filtering capability.
One problem is that these are not sold anymore. Other brands i found did not have mesh as fine so i found an alternative.
"Silver screens". Those are DIRT CHEAP and are screens only (exactly what you need) and will work just as good.
I buy brass plumbing head caps similar to whats on the picture below. They are hollow inside and allow me to place filter inside without any retaining ring/clamp (what ever you call those) making it even cheaper.
I simply cut the needed circle and place it inside.
Clearing it out is as simple as pulling it out when hot and giving it a blow with a blow torch. Then put it back in and its ready to go again and again and again.
my 3d models http://www.turbosquid.com/Search/Artists/tonycstech