I use a mesh recommended to me here on OCN, links previous posts, from themeshcompany. It's a stainless steel mesh, they have open area 60-64% and you can get mesh size #100 to #200 in that maximum open area they offer. It sure does block pressure, but then so did the stock filters that were awful
I went with the most filtering #200 option which is similar to Demciflex or better.
Demciflex is only soft frame magnetic and expensive, similar filters in size from Demci cost $35 without shipping.
I paid around $24 including shipping that was more expensive than the A3 mesh, plus I have enough left overs to make 2 extra dual 140mm fan filters and 2 extra dual 120mm fan filters since I got 2 A3 sheets for price of 1 of the same mesh and I only used about 35% of the total area I bought.
Clotch is not gonna cut it, or curtains, it doesn't have the open area %.
This #200 mesh is so fine the wire it's made from is like hair, so thin you can barely see it, which is good and bad, good for the filter but bad to clean up and see, plus it's conductive so one has to keep a track of where that crap flies. Good thing is it's very easy to cut, hell even easier than paper to me with a modeling knife.
Temperature on my soldering iron I've had set to about 210 Celsius. I didn't have to fill the whole area but once you have the edges there is really not much left so I melted the whole area so the filter is attached everywhere. The frames bent a little under the heat and pressure applied but it actually made them much easier to take in/out
I've waited like a year to do this mod, in the end I just couldn't stand the sight of all the dust in the case and how useless the stock FD filters are.