Need a flash

Your camera manual will explain which flash modes are available to you. Better start saving for a K20D I guess . . .

For slave1 mode the flash needs camera information so if your camera doesn't have infared it can't send it to the flash, it's as simple as that.
Also with the K10D for example it still needs the build-in flash to set of the flashgun, with the new firmware you can set the build-in flash as controller now so you don't see it so much in your photo.
Also with two flash guns you need an controller flash to set the other off I believe.

If you trully want to use only one flash off from the camera you need to wire up, just like you said. You can also use a RF or IF transmitter on your camera hotshoe and one on the flashgun, you basicly have wireless then also.

any recommendations on those transmitters? Or a wired solution at all?

Then I'll start saving for a K20D... maybe when I'm a bit better!

When the new Pentax hits the market in a couple of weeks, you will see a flood of used K20s hitting the market at good prices.

Been doing some research but not coming up with much.

With my current set-up (k110d and af-360fgz) what do I need to get to keep the auto settings when the flash is off the camera? I'd just like to experiment with different portrait lighting.

If you want to keep P-TTL capacity then you'll need *another* 360 (or 540 or similar) to act as master. If you're prepared to work the flash in manual mode (which is what you want anyway in studio work for repeatability/tweaking reasons) then you'll either have to:

a) Get some sort of remote firing system (search for Cactus V2 on eBay for probably the cheapest solution).

or

b) Buy an old manual flashgun to sit on the camera and trigger the 360 in Slave Mode II (see the 360 manual for changing slave modes). The on camera flash won't work as it will trigger the 360 on the pre-flash (which can't be turned off as the built in's P-TTL only).

Worth doing though! Off camera flash is so much more flexible than on camera

Yes definately. I was looking at those V2's yesterday and noticed they actually have V4's out now. They seemed to have improved the antenna compared to the V2's. So I may get a set of them. They are about the same price. I'd rather just use the off camera flash tbh, I prefer the lighting it gives!

Got the V4's. A lumiquest softbox, a stofen and the af-360fgz.

Should be a fun weekend!

Indeed, have loads of fun with them ^^