I have the benifit of a compressor so this was how I was going to pressurise my reservoir.
The first thing I did was to find a suitable threaded air fitting small enough to fit to my old clutch m/c lid. I then drilled a suitable hole just smaller than the thread on the fitting:

The top of the lid will probably fall off which isn't a problem, infact its probably preferable. I then screwed the fitting into the lid, cutting a thread just with the thread of the fitting. This created a good seal but you could put some silicone round if you needed to:

This needs to then be screwed onto the master cylinder:

Now for the compressor. Only a small amount of pressure is required, I set it at 10psi no more than that is required.

To apply the pressure I have an airgun with a rubber nozzle, this is best as it gets a good seal around the fitting in the reservoir cap.

Now set up the slave cylinder as you would normally with a rubber hose on the nipple into a jar/bottle

Now crack the nipple and apply the pressure to the reservoir. You should see the fluid start to drop, if not you can do up the nipple for a second with the pressure still applied then crack it again. Mine started flowing by doing this. Either way it didn't take long for the fluid to start coming out of the pipe and into the bottle. As soon as it does, with no air in, tighten up the nipple and remove the pressure.

After everything has been finished remove the modified lid, top up the fluid as required and fit the standard lid back onto the reservoir. You should now have a nice firm pedal with a clutch in full operation.
This process can be used for bleeding the brakes also. If a compressor is not available then a pressurized weed killer type item can be utilized to work.
If anybody has any questions about the method then please ask. I have tried to explain it clearly. Hopefully this can be useful to some people
Craig