RobK wrote
instead of soldering all the grounds to a pot, can I do connect it to the shielding - by soldering all the ground wires onto a washer, then screwing down the washer onto the shielding and into the body using a small wood screw?
You can yes.
I do something similar using a solder lug between the pickguard and switch (on one of the switch screws) and the lug then connects the pickguard screen to earth. The pickguard is fully screened and the pot covers and cavity screening are connected to earth via the pickguard screen (the cavity screening folds over a little onto the top surface of the body so it contacts the pickguard screen). I connect the trem earth wire to the cavity screen with another solder lug and a screw. This all means no soldering to the back of the pots and no earth wire from the controls to the trem claw.
