I have an acquaintance who uses a exotic solder that on a/b comparisons beats anything I have ever heard. He willingly will solder up cables and connections for me, but will not reveal what this solder is. Finished joint/connection is a dull grey, not bright and clean as you would normally expect. Could also be an exotic FLUX/cleaner. Would like to do my own soldering, as his time is very limited, and sometimes the wait is considerable.

Would appreciate any suggestions or leads. Thanks:
Dull grey is an obviously cold joint so that's what I'm going to try for from now on!
Dull grey is a cold solder joint if the solder has resin in it. Almost all solder's do have resin. Properly soldered joints force the resin to the outside of the joint and they wind up coating the joint and creating a insulation on the outside--a protective coating to reduce corrosion. A solder that is dull grey and is properly done, must not have this resin. I'm not familiar with any solder like this, but to some degree it makes sense. Resin is an insulator, so a joint with no resin could be better than a joint with resin. The only downside might be the long term effects of a solder joint without a protective coating. It would also be interesting to see how one would use such a solder, as without resin the flow might be difficult to handle (I don't really know since I've never even seen solder like this--and don't even know if it exists--just guessing by your description).

This is mostly speculation on my part--but it seems plausible.
Sinbad, I suggest you try samples of TRT Wonder solder and the WBT solder. Both of these are wonderful, and make a stunning difference in the sound when used instead of the common variety. If you cannot find these two, I can send you a small sample of the TRT for sure, and perhaps the WBT. I will have to look for the WBT, I am not sure I still have any around. Let me know if you want to do this test for yourself.
What is it about my offer to give away free solder to a fellow Audiogon member that caused me to receive minus votes?
Go over to AudioAsylum, search 'solder' on the Bottlehead forum. More info than you ever wanted on types and techniques. Cardas, Wonder and Radio shack lead free with 3% silver seem to be leading the league.
Albert: Must have been one of those "solder is solder" types. You can also bet that they do not work for NASA in an electrical facility.
Just a note...lead content solders tend to look very shiney and silvery and smooth when done well. Lead free solders are usually duller (grayer, by your definition?) and don't look as liquid smooth, even when properly done. They have a very high tin content.