I don't believe there's a way to do it without putting them in squads. On the other hand, merely putting them in squads with a uniform assigned and leaving them inactive does indeed seem to do the trick. If I remember right you have to activate them once so they'll skivvy down and put on their uniforms, but then you can deactivate them (using the "inactive = uniformed" default option) and they'll do the right thing.
I only experimented with the technique once, though, for two reasons. First, it's been quite a while since I had a fort live long enough for embark clothing to start to rot away, and second, I was completely unable to crack the problem of being unable to keep track of which squads had civilians in them and which were real military. Absentmindedly dispatching my squad of wood burners, lye makers and soap makers to deal with a greenskin ambush and not realizing it until all the pretty purple messages came in put me in the mind that I'd created a larger problem than I'd solved.
So for me, I'm basically ignoring the problem until clothing gets fixed in a future version (fingers crossed), and making shameless and judicious use of the dfhack clean and cleanowned "cheats". It's by far the part of the game I'm least happy with, but I mean … come on. Last night I had my squad leader axedwarf take two bowgob arrows to the upper arms and lop off the head of the offending greenskin with one stroke, achieve axe lord status at that moment, name his axe and then immediately take it to the barracks and go to bed with it. Quibbling over socks strikes me as unappreciatively petty.