The center tuning meter adjustment usually does not require any test equipment. You usually tune to a quiet part on the dial(only white noise) and adjust the discriminator(quadrature or ratio detector) for a zero across the meter. You have to have the correct nylon tuning tool for the core that is used. be careful that these transformers have usually 2 cores, one for a zero and one for linearity. One usually adjust both of them. For linearity, one uses as IF sweeper to set "S"curve buty best method is to measure mono THD and adj for lowest THD.
The signal strength meter is adjusted with a set input RF level.
The signals to these meters usually go through switches, so they should be cleaned as well as part of a tuner tune up.