I have heard good things about FI's sealant so it would be a good option to go for.
Yeah, not too sure about the 4 micorns. A japanese manufacturer which sells their own range of nano sealants reckons it does but it would be too hard to test as paint surfaces are inconsistent.
There is a product called Gtechnique from Germany (i think) which uses this nano technology and it comes in a clear liquid form. Great sealant but very expensive. Around $120 for 250mls!