For dual titanium, I like 26AWG, and 8 to 10 wraps depending on the atty. I
greatly prefer contact coils when working with titanium, but they do gunk up faster than spaced.
Here's a good guide on contact titanium building, by the way.
As far as cleaning, it's easy enough, just like the guide above instructs you when tweaking your coils, use 6 to 8 watts in wattage mode,
pulse it until you get a very dull glow, don't ever go for a bright glow, burn off the gunk, take a brush to it inside and out, re-wick, job done. For extra cleaning, wet the brush with isopropyl alchohol, give it a good scrub, then pulse it again a few times to burn off the IPA residue, or just wet the brush with water and use a bit more elbow grease.
For brushes, I really like these, good for 2mm ID up to 3.5mm ID (plus they're REALLY good for taking care of your gums!)
For stainless steel, 430 is my favorite, I think you'll find you have better results in TC mode compared to 304 or 316, since the TCR of 430 is higher and is less effort for the mod to accurately regulate.
Unkamen carries 28ga 430SS, which is ideal for twisting, and at $10 for 200 feet, it's dirt cheap too.