a different shower problem

My guest bathroom shower has not been used in over a year. When attempting to get it ready for guests I found very little water coming from the faucet. In fact, better pressure from the shower head than from the faucet.

Sounds like your diverter may be stuck.

Is it a tub spout diverter or a diverter valve?

I'm sorry but I don't know the technical terms; To turn on the shower, you lift the diverter on top of the faucet

What you're calling the "faucet" is the tub spout. Thus, you have a tub spout diverter.

I believe that is where the problem lies.

Remove the tub spout diverter and see if you have normal pressure coming from the stub-out (the pipe that the spout is connected to).

Look for a hidden set-screw. If you find one, you'll need the correct allen wrench to unscrew it. Then pull off the spout. If there's no set screw, you can unscrew the spout using a large channel locks with a rag underneath (to avoid marring the surface).