I started riding fixed a week ago for the first time in my life. (Amusingly, I am forty-seven - "I still feel that variable gears are only for people over forty-five").
I am as yet unpranged (it may help that I own a tandem so I'm used to the pedals occasionally trying to do their own thing whether I wanted them to or not), although I've had one pretty good go at it - a ped did the "will I cross, won't I cross" thing, I slowed to a crawl; with a freewheel you can coast right pedal down, out of the saddle, left foot free, stop any time you like; when it became clear I'd have to stop I was still in the saddle at an awkward point in the pedal cycle and nearly fell over sideways.
Initially, it was a complete mystery to me how I am to get my left foot into the toeclip. (At the moment, the pedals have clips but no straps, which seemed like it would be easier; and FTAOD I've been riding freewheeled bikes in toeclips for decades.) I asked a reddit sub and got two replies one of which was to the effect of "set off very slowly". That works, but on an urban commute it's not always ideal, and normally one of the advantages of toeclips over clipless is you can hammer away from a start without having to faff about clipping in.
There some kind of knack to doing it at speed, or is it just practice, practice, practice?
(I really am not going to switch to clipless.)