Just putting the saw down on some soft wood so the teeth dig in would probably work. Otherwise, stick something in the teeth or a hole in the blade to keep the blade/spindle from turning.

:You could lower the blade, and install a "C-clamp" carefully, on the blade, positioned to avoid the teeth. Now you can rotate the blade, until the clamp meets the baseplate, and now you have a locked spindle.

With saw unplugged or power removed I just clamp pair of vise grips onto the blade, using the vise grips wedged against the saw or hold it and break the nut loose. Same thing as above avoid the teeth on the blade or it will CUT you!

I'm having problems getting the nut to come out. I've sprayed it with WD-40, I've got the blade clamped down so it won't move. The nut is turning, but it won't come out. I'm baffled as to what is keeping it in.

The shaft from the motor is probably turning also. The nut needs a blow or shock to break it loose. Use a box-end wrench or vise grips on the nut and give a good blow/hit on the wench toward off with the blade locked in wood in a vise or sitting on soft wood.

Yes lisa I lock the nut hard and push it to the left and then puah up and down in and out till it cums all out hope that helps