Purging with CO2 cartridges

So, I'm about to make the jump to kegging.

I got myself one of those CO2 cartridge kits for a trip up to northern Wisconsin. My questions:

-If you're using CO2 cartridges for dispensing only (as opposed to a tank) do you still use half the amount of priming sugar you would use if you were bottling?
-Is there any way to purge the keg of oxygen when I rack? I know most people purge the keg after racking, but I don't have a tank (yet). Should I rack, and then just leave the top open for a few? Or should I hit the keg with a shot from a cartridge before racking? Any ideas?

you should use aprox. 1/2 the amount of sugar you usually prime with when priming a keg and YES i do suggest you hit the keg with a few shots of co2 from a cartridge when you rack

Before I rack? Or after I rack? Should the cover be on so that the o2 can escape?

I imagine it will all come clear as I'm doing it.

I wouldn't waste your money.. I'd just wait until you get a regular tank and regulator. You *can use those cartridges, but its expensive. They work great for parties, and thats about it IMHO.

I think you should go ahead and prime the keg, and then close it up. Give it a blast of co2 from the cartridge, then vent it (through the pressure release valve) and then give it another blast. That should purge the keg and displace the 02 with co2.

Where and when are you going to northern WI?

Up near Conover about a mile down the road from the UP. My boss has a cabin up there, so we basically go up there for a few days and drink ourselves stupid. This year I decided to take my own beer, and rather than waste a bunch of bottles (all trash goes into the campfire), I figured it was time to keg.

As far as giving it a blast, I'm using those little CO2 cartridges. Does that mean I would basically be using 2 cartridges to purge the keg? That seems kind of wastefull. There isn't really a valve to do that. After I purge, can I remove the disconnect? I guess it doesn't matter, I'd just rather take it off so I don't risk knocking it.