I tend to use crocodile clip cables to connect conductors together, however for the IR test on a single circuit you would need to remove the L and N from the terminals, though you could drop the N into the MCB, leave cpc connected to the bar and just clip your probe onto the bar.
For a global test then link the bus bar and neutral bar (once isolated!) and clip your probe onto one or the other, I occasionally do a continuity test if I am unsure if I have good connection with the link cable.