Some of my experience, in case anyone finds this useful:
I have used Future (the real thing, that I got in the US a long time ago) for many years as a barrier coat before decalling and washes, usually over enamel paint (Humbrol, Tamiya Enamel, Model Master, etc.) It was good stuff, but mine started to run out, so I started looking at alternatives a few years ago. SprueBrothers used to also sell the real thing, rebottled into a smaller bottle and at a relatively high price, but it is still a way to get a hold of the real stuff. I haven't checked recently whether they still sell it, but I remember they had no problem shipping it to SA since it is not flammable. Humbrol Gloss Clear seems to be very similar, and it also works for dipping canopies, etc. I have a bottle of Humbrol Clear, but since I still have a little bit of real Future left, I have only done a few experiments with it that seemed to confirm that it behaves the same as Future. I have tried most of the local floor polishes (Pledge and Mr Muscle), but none of them seem to really work the same as genuine Future.
More recently, I started using Tamiya X-22 with their own acrylic thinner as a clear coat before decalling. This is my new favourite as an acrylic clear coat - it seems to work better when spraying than what my experience was with Future. I always felt that I had to use a lot of Future to get a proper smooth finish, and the thinned Tamiya X-22 seems to give me the same effect, but with fewer and thinner coats. However, this is when you spray it. If you like to brush it on, Future or Humbrol Clear probably still works a bit better.
For final coats, I used the Humbrol Clear Cotes (the ones in the 40ml bottles) for a very long time. However, I ran into two problems with them: The childproof lid on my bottle of gloss got very tight and became almost impossible to open. I tried everything, and eventually, out of desperation, I dipped the cap in boiling water, which eventually allowed me to open it. Although that got the bottle open, the heat from the boiling water immediately yellowed the contents noticeably. Humbrol changed the design of their childproof lids, so I don't think this will be a problem for others who purchase it now. It doesn't seem to yellow under normal circumstances, so I think it is still a good top coat. In my case, however, it resulted in me having to throw the bottle away. The second problem was with my bottle of Matt Cote: The stuff thickened so much over time that it became almost impossible to stir and mix properly. Another problem, probably less serious, with the Humbrol "Cotes" is that they are normal enamel paints. That means they soften again when you apply any enamel thinners to them - really not a problem when they are used as a final coat, but I sometimes used them as barrier coats when figure painting, and applying thinned oil paints over them would dissolve them quite quickly. That is more of a note about their use than a real problem, but it is a slight limitation on their use.
After the issues with my two bottles of Humbrol Clear (and note, this happened after a long time - maybe 5 years or more), I decided to try the new Alclad Lacquer clear cotes. The stuff is incredibly expensive in SA: About R160 for a 120 ml bottle. It is around $10 in the US, which doesn't sound like much, but when bought in SA the bad exchange rate really made them very expensive. However, I can confirm that these clear coats are the most fantastic clear coats I have ever used. They are lacquer, but a relatively "soft" lacquer, so they don't seem to attack either acrylic or enamel paints. You spray them straight from the bottle without any thinning, and they are intended to be used that way. It dries to the touch in minutes, and cure in about 1 hour. I have the gloss and matt versions, but you also get satin, flat and a few other inbetween versions. The gloss is super gloss, and sprays absolutely wonderfully. You seem to need to apply very little to get a true gloss finish. The matt is like magic when you use it - it goes on very thin, but it really looks like you just erase the glossiness as you apply it. The matt still has a very slight sheen, which I like. If you want true "flat", their "flat" is apparently a better choice, although I haven't used it. Being lacquer, they seem to be relatively impervious to most enamel thinners, although you probably need to experiment to make sure. I can really recommend them, although the price is really scary. I bought the gloss when my Humbrol gloss bottle yellowed, and the matt when my Humbrol Matt became too thick to be usable. However, I like them so much, that I think I will buy the satin also as soon as I have an excuse to use it, even though my bottle of Humbrol Satin is still fine.
Anyway, this is just my experience. Note that I spray my gloss coats on - as I said, if you prefer brushing it on you will probably want to stay with Future, Humbrol Clear or other acrylic based clear coats.