Pixel soldier triggers don't support rear curtain, hss, etc. Your trigger needs to support it, and so does your flash.
You'd need Pixel Kings, YongNuo 622c, or similar triggers that have that capability. If you're on a budget, I suggest the YN622c trigger set. It's cheaper and you get more bang for your buck than the kings, and with the right flash, supports menu setting flash changes.
Keep your pixel soldiers though, in case you want to remote trigger your camera/flash chain (i.e. Your pixel soldier plugs into only the shutter release port, tells the camera to fire remotely, which fires the YN622 or pixel king or whatever trigger in the hotshoe, which sets off your flash(es).
Thing is with the YN-622C second curtain only works if you have an eTTL flash connected to it and not a dumb manual flash. (At least not for me) Which again is fairly stupid. I mean for a multi-flash setup I really don't need intelligent eTTL flashes at all. A 'dumb' manual unit is much easier to work with anyways, but of course then I can't do second curtain again
Well, the flash must support second or rear curtain sync too, or it isn't there to use.
You would also have to turn off wireless in the camera flash menu, and have a 622 on each remote flash, and one on the camera. The rear curtain sync option only appears when you have turned off wireless in the menu.
You also have the option of purely manual flash with the YN622, as long as the flash supports rear synch too. You can either do it so you change manual power levels and zoom through the camera menu, or you can go full manual and fix it so you only change power/zoom on the flash itself. I do the latter all the time, it's faster to push a button on the back of the flash quick than to go digging through the menus (for reference, I use the YN568EX). And I when I'm doing that, I'm shooting rear curtain sync.
If mixed mode won't give you both manual flash and rear curtain (never tried this myself), then you can mix it up with your triggers instead.
For example: I have the RF602 dumb triggers (fire only, have the cable for remote shutter release). If I put a YN622 on top of the camera, and then put a dumb RF602 fire only on that on camera YN622, I can then put a TTL flash on the remote 622, and I can put a manual flash on the remote RF602. You should be able to use your pixel soldiers the same way I'd imagine, the YN622 atop the camera ought to pass the fire command through just fine. That way you use your dumb triggers in the mix to fire manual flashes. I have successfully done a double flash fire this way (YN560 full manual flashes go on the RF602s, and fire when the shutter opens, YN568EX flashes go on rear curtain sync and fire just before the shutter closes).
Bear in mind you cannot do this with the pixel kings (the hotshoe on top does not support a flash so I doubt it'll pass through a fire command).