Dan Durston, I recently seam sealed a tt rainbow with permatex, it's fine, either use the method this person did, which isn't a bad idea, given you'll get finer control over the dispersion, or just squeeze out a very narrow bead using the applicator tip cut very small opening, then rub that into the seams and spaces in the seams.
Permatex is easy to work with, and as I saw noted in various threads on mixing up your own batch vs permatex, this stuff is actually designed to be flowable, whereas the mixtures people make using silicone/thinner aren't, GE I seem to recall specifically states that thinning silicone per se isn't recommended because it won't be the same in terms of durability. Can't remember the specifics but it made sense to me.
My feeling after watching how tt seals theirs vs using permatex is that it's the same old issue with seam sealing on a commercial level (and why back in the day, pre taping, tents were almost never seam sealed on purchase), speed/efficiency/cosmetics vs performance and durability. Ie, it's super fast to put on a thin mixture with that applicator, even if that mixture won't last that long, and that thin mixture is almost invisible on the tent after application. Permatex is most definitely not invisible, but why should anyone care about that unless wanting to resell at highest price. Personally, I'd rather get a slightly messy looking but durably sealed tent than a tent where I have to redo it over flaked off silicone remnants. In the future I'd pick a permatex sealed tent over a mixture sealed one, in general, it's just not that easy to mess up with permatex, the stuff is easy to apply and spread, and it's not really possible to mess up the mixture process since there is none.
I found it very hard to avoid dripping when using the tube directly, because the stuff keeps flowing a bit after you lift off the applicator tip, caused some drips on the tent, but again, who cares, those spots are now just more waterproof, after I smeared them out, heh.
I rubbed in the permatex with my finger using a cut off tip of a mechanics latex glove to avoid skin contact, and did it outside.
The tent dried / cured outside in the shade mostly during some sunny days recently, and came out with no tackiness. On the other hand, I've sealed some silnylon rainpants I made just to see how that would work, and dried/cured them inside, and the seams were a bit tacky, but nothing requiring talcum powder to deal with.
If you can't find permatex, which I had difficulty locating, there's another product out there at auto parts stores by another brand, also called flowable silicone, and I read both msds pdfs, they are clearly the same, and probably use the same fluid from the same source given how identicaly the data sheets were.
I didn't really care about the weight but I think it might have added an ounce or so, but I did a very robust sealing job because the rainbow has some difficult stitching re full sealing, so I did some areas inside and outside, and used a fair amount of the sealer. In general the listed weights on tents should always be given with +-5%, that's a law in Norway, you can't say something like this weighs x grams, it never does unless it's a coincidence, you have to say it weighs x grams +-5%, or maybe 10%, can't remember, I know my tt rainbow weighed about 2oz more than listed on tt site prior to sealing, materials vary slightly.
I'd also say that the permatex definitely has increased the strength of the seams/stitching, it's thick enough to really be noticeable when it dries, I can't really see the super thin mixtures strengthening the actual stitching that much, mabye a bit, but not a lot.
[checked]Oh, I checked, the tube is 1.5 ounce net, I used probably about 1 oz total sealing the rainbow, maybe a bit less, since the same tube also sealed some rain pants and most of some pouches I'd made. I don't know how much weight silicone loses when it cures, must be something, so I'd say it's safe to say the tent gained maybe .75oz total, and that's with very solid seam sealing, including, following franco's advice, the bottom seams and tieouts.