Eh, I get rusty in ALL games. Though some of them are easier to pick up again. I don't know what makes it harder or easier, its just works like that. Anyway, my biggest problem with DF with last times I've played it has been that I've been unable to keep being interested in playing it longer times as I'm fricking sick of Forbidden beasts.
Anyway, I should probably learn ways to make my fortresses more faster and efficient, but so far my standard play style is this:
As soon I embark I dig myself opening to my fortress. First floor down from entrance is one with all stockpiles, second one is the one with work shops, after that come sleeping quarters and after that one I create room for socializing. Somewhere between is a hospital I also tend to dig until I find caverns so I know how deep they are. On the entrance I build trade deposit and workshops that can cause miasma inside like tanner's workshop and butcher's work shop, with next to them being corpse stockpile and refuse stockpile. Then I try to create trap zone on the entrance and way to keep my dwarfs save from sieges. I get food from hunting, butchering useless animals and farming, either by creating simple pump and getting water where I need it, by digging and using flood gates to get water from pools or in the caverns and from trades. I usually when I'm not rusty manage to have enough food and alcohol, but my military is bit weak though they are still usually capable of defeating FB that don't cause syndromes which takes effect right away.
Since I'm bad with pumps, I don't dare to do magma pumping as my water pumping is already disastrous so I only use magma by digging to lowest floor and getting magma forges and other magma workshops there. I sometimes put stockpiles next to them so they would be little faster, but its still annoyingly slow. I did once for fun create magma flood gate I used to kill goblins from sieges I caught, but thats it.
I try to survive in caverns by walling off the important sections from other parts, but forbidden beasts sometimes find the way in that I didn't notice. Usually because I try to expand in the caverns and they attack on bad timing. Beasts rarely are themselves bad, but the syndromes tend to kill me.
So yeah, when I'm not rusty, pretty much only thing that kills me are syndromes. I also should probably figure out how to create more efficient fortresses, but I've manage.
Heck only things I'm unable to do is find megabeast in fortress mode without embarking on caves and making fortresses on sites with aquifer
I have tried the cave in method and it worked once, but most of time there are multiple layers of aquifer so it doesn't help much.