I don't doubt the effectiveness of Tenax. It's very nice to melting seams, but I'm not sure how you get it to substitute for Tamiya Instant. (Actually I have found for some joins that orange cap Tamiya is actually better: sets slower but is very strong. Not a substitute but a complement.) I find Tenax sets so fast that by the time I try to join the parts, it's half dry. Maybe I don't use enough? And I've just bought some Mr. Levelling Thinner - not the first time you've cost me money. We'll see if it's better than Tamiya lacquer which I have used with great success in the past at very low ratios. And I like your tip about cloth dremel tools for buffing.
Despite this talk about Mr. Color (I have maybe 60 bottles of Tamiya or Gunze paints and am not going to throw them away, so it's worth it to look for the ultimate thinner), whenever possible I'm moving toward water based acrylics. This is a completely personal matter for me and I would only recommend it to the people who like messing with paint and don't mind a little learning curve. I have some Citadel which I like, but my real favorites now are Vallejo Model Color and Golden Fluid acrylics. One does need to master artist acrylic airbrush mediums to make this work. But if you do, the resulting paint is wonderful to work with. No odor, lovely pigments (I'd put Golden's up against any paint I've seen) and if you're blowing them thin at about 15psi - where I do most of my spraying now - they will not clog. By using hardeners, retarders, "flow aid" and the main thinning mediums you in essence create your own paint for any given project. I know all Goldens use the same agent so they mix perfectly and I'd guess strongly the same is true with Model Color. (Might note that Vallejo makes a lot of art paints.) Mr. Color does almost all of the standard military colors, but I've found that as I learn color mixing I can get very close to almost anything I'm looking for with Goldens. With the right mediums you can spray at extremely thin ratios at low psi. The down side is that they will take a little longer to dry. The upside to that is if a spray goes wrong, you've got a few seconds to simply wipe it away. Obviously if you're using any of these, you don't have far to go for hand brushing. And the stuff all comes in dropper bottles, lasts forever and is dirt cheap. If you ever try them out do not thin with alcohol ever - this is death - and never use more than a few drops of water, more will break the integrity of the paint. Use water if you want a wash: check Swanny's for a couple of good "sludge" wash recipes using artist acrylics: there you actually want to break down the paint. And don't bother with the cheapo craft paints that are almost free: here you get what you pay for. Golden or Liquitex cost less per ounce than model paints anyway.
I've noticed one thing about these paints. When first applied they look more like a coat of paint over a surface than having the plastic change colors. A modern car has the colored metal effect. Military weapons, at least in the past, didn't. (NMS excepted natch.) They look like metal objects with a coat of paint over them. I hope this doesn't sound nuts, but think about this the next time you look at a restored warbird, tank or even museum ship. By the time weathering is done the effect is less evident, but I think the water acrylics just have a different "look" and I think I prefer it.
And it cleans up with water or windex. I still use lacquer thinner to clean the airbrush though. These paints use liquid polymer as agent - essentially really thin plastic - and solvents will break them down immediately. That means you don't use solvents for thinners, but when you're cleaning your nozzle, nothing better than to break down paint. I learned early on that just because this stuff is so benign, and seems to blast out clean quickly, that you need to give your brush a good cleaning after every session - having liquid plastic as an agent could leave a clogged brush very quickly. But it cleans easily if it clogs: just don't forget about it.
BTW: if you drop by the art store or check the blick web site you might check Sennelier dry pigments. Some paint loonies in the art world still make their own earth tone oil paints and that means they need inorganic pigments. (Ground up rock or minerals.) Sennelier provides about ten colors: I think ochre, raw umber and burnt umber will take you a long way. I'll be getting both black and white also. They're more expensive than MIG but about one third the cost per volume. As for quality - Sennelier is the probably the most famous high end artist paint maker in the world - so the stuff is remarkably fine. They're almost tricky to use because they're so fine but are great if you're setting them in alcohol or mixing them into some kind of brew.