Rear curtain synch by hand

O.k. Here is my dilemna.

I was out shooting on Mardi Gras with my N80. Just doing some street shooting. Letting the camera do most of the work (I know...I know....lazy, but I go for speed when I shoot on the street and I use Aperture Priority NOT a program mode...so it is just a venial sin... ). I came across a fire act and decided that this called for rear curtain synch. This is where the camera meters for ambient light when the shutter opens (first curtain) and then right before the shutter closes the flash fires (hence it is in synch with the rear curtain).

This gives a really nice effect if used well. As you can see in the attached image. It can freeze a dimly lit subject, but create some nice blurs on bright subjects. Like in this image.

Now this is all nice and fine when my camera does the work, but how can I get this look WITHOUT automation? Like on a 4x5 or even my ETRsi? O.k. I know that TECHNICALLY they don't have curtains, but still. Any hints on how to do this in the studio?

Thanks -

Oh, and here is that image....

Depending on the shutter speed, you can just fire it manually.

I think the Pocket Wizard will let you do end-sync with a long exposure and a leaf shutter lens.