I'm with IO540 and Cusco. Get a new instructor, 2 sorties of instrument training with no teaching or demonstration of instrument checks this idiot is bad news.
Check everything that can feasibly be checked, before brakes-off.
DME - ident, check for sensible reading
VOR(S) - ident, check for sensible reading(s), cross-check if multiple instruments, check 5 and 10 degrees off radial and on reciprocal
ADF - ident, check for sensible reading, switch to ANT, check points at antenna wing (normally port)
GPS - check receiving and giving appropriate position report
Displays - flags out if idented
AI - erect and caging (unless venturi driven)
DI - stable
Altimeters - cross-checks, within 100ft of each other and airfield elevation correct at airfield QNH
Then when taxiing, check during turns:
- ADF tracking
- DI & compass tracking in turn
- Turn needle into turn, slip ball out of turn
- VOR displays remaining stable
- AI remaining stable
To be honest, I'd do all of this and teach this for VFR flights as well. If the kit is in the aeroplane, the pilot should know how to use it and whether it is serviceable or not. It is merely more important for IMC flight.
G