I remove the hand wheel completely and use a polishing grit sandpaper on the inside of the hub and on the shaft onto which the hand wheel hub slides. This removes grit and grime. Put a drop of oil on the shaft before reinstalling the hand wheel, give it a spin and then reassemble.
Also the bobbin tire can be too tight against the hand wheel, Surprisingly this can put enough pressure against the main shaft and turn the machine even though you have the clutch knob loosened.
If you have the screw for needle thread guide you can bend a new one from a paper clip.