"How do I soak the clutch with WD40?"
Orca, no need to do that yet.
First, try Mac's technique. If that doesn't work, try Karl's ... which is one I had to use routinely on one car I owned and now usually try first. If you start it in gear with the clutch depressed, keep the clutch depressed, but be sure you're comfortable driving that way. You can easily pull it out of gear into neutral while running if you have to ... just make sure you have plenty of clear street ahead of you.
Other guys like to jack up the rear, start it in gear, clutch depressed, and jam the brakes on.
I discovered the WD40 method after wearing myself out on a '37 PU. I tried every method and had resigned myself to pulling the transmission. I soaked the clutch down through the inspection opening and went home. A week or so later came back to find the clutch loose as though it had never stuck.
I have also had numerous "frozen clutches" on engines that had sat a looong time and that involved extreme rust and corrosion. (For guys who have done it, how about a French Vedette "V8-60" with an aluminum transmission case and bell housing, everything rusted solid including the pilot bearing and engine itself ... almost no access to the diaphragm bolts.)
Your situation does not sound very serious since the car was driven recently.
( ... "French Vedette "V8-60" ... See, Brian, THAT was a below average day.)
