first off riding no clips AND brakeless and then posting this thread means you need to get your self a front brake,...seriously dude, the bus/ups van/garbage truck doesn't care that you can't stop fast enough to avoid it.

ok sit down skids: the way I figured this out was: I stiffen whichever leg, as that pedal is coming upwards, I let the pedal lift me slightly off the seat, and this completely unweights the rear wheel, and it's easy to lock it up from the
seated position or just skip it and do the same thing again as the other pedal comes around, THAT stops you going down hills WAY better than just skidding.
(theres probably a name for it, but I'm ignant )

I used to do "jamaican skids, mon" (I was told this trick here) where you hook your foot under the front pedal, and then push back on the rear, but if you run cage pedals like I do, your going to need a new pair of shoes each week, as the shoe tops just get cheese grated.

ok I HATE CLIPS,...or thought I did,..THEN I got some GOOD track pedals with steel clips, and GOOD leather straps (soma hellyers, no name clips, soma double straps), and they are just so natural and easy to kick into (you don't have to look 95% of the time) now I don't mind the clips so much, in fact I'm gettin to kinda LIKE IT as now I don't have to lug around a pair of walking shoes (I tried running clipless for a while too)

this is what got me hooked on riding fixed, I had to "learn to ride" all over again