I'm not sure which technique you are working from, but there is only so much that you can do. If you want to reduce the noise, you need the loosening action as described by Erdnase. Not necessarily his grip, but the loosening action kills almost all of the noise for me. This introduces the knuckle-flash however, so it isn't as pretty visually. If your pulling strike-type bottoms, you can do it quicker and without the flash, but I've always had way too much drag due to the angle of the emerging card relative to the deck (meaning: it's scraping against the deck the whole way out and making all sorts of noise).
I am no expert, and I am sure that it is possible to reduce the negatives of both of these approaches, but I see it as a balancing act. I try to get the best of both worlds. Get enough loosening to reduce the noise and keep as much as a strike action to it as possible to avoid the flash. If you have to pick between the two - however, you should pick the noise as the one to eliminate. I believe that it was Aaron Fisher who said that a pass is like a child: it's better to be seen than to be heard. Slightly different context here, but same point. You can compensate for the flash by watching the angles. If you have a decent rhythm, most laymen won't even notice a flash or recognize what it is if they do see it (no one watches GPS for fun) Anyone can recognize the noise and realize that it only pops up when dealing to yourself or one other person. It's like ringing a bell. So I'd lean toward a quieter deal rather than a more invisible one.
One thing that worked for me for a while (after Erdnase and Strike-Bottom dealing as basically described by Jason England here) was the bottom deal discussed by Vernon in his inner card trilogy. I believe it is in More Inner Secrets, but I could be mistaken. It works from a straddle grip and I thought that it allowed for a good balance. I've changed it up a bit, but the angle and pull on the bottom card are pretty much the same and, thus, pretty damn quiet when I get in swing.
