Piccadilly has a pick up area, and would be preferable to Oxford Road if coming from the M62 by any of the recommended routes, including lapping the M60 and coming down the A57(M).
If he comes in via Ashton Old Road then come up the A6 London Road he'll need to do a small lap round, or alternatively coming in via Ashton Old Road will land you on Fairfield Street without using the Manchester/Salford IRR (Great Ancoats Street and Mancunian Way) the approved pickup point is in the Fairfeild Street Short Stay car park, but if you want to be avoiding using that, then parking/stopping on street around the station areas is easily possible, if you know where you're going.
Examples of easy to find places include:
Travis Street, Store Street and Boad Street, the "Quickest" of these for you to get to from your arrival platform, Platform 13, will be either;
Store Street (Under the station approach, there is metered on street parking but you can sit and wait without too much hassle)
Baring St / Travis Street, be aware this is usually populated by taxis queuing so I wouldn't personally recommend it.
Or anywhere round the Eastern end of Granby Row (This would be accessed from the A6 London Road Northbound by turning left immediately before a the set of traffic lights at London Road / Fairfeild Street) and is easy to access, as easy as Store Street for both vehicle and pedestrian, if using this area, what I would personally recommend, exit Piccadilly Station from the Fairfeild Street Entrance (Under the station, infront of platforms 9/10 there is a stairway through the floor, follow this to the exit (it is signed as such and for Metrolink) exit there, and cross corner to corner for the set of traffic lights, and head between the Best Connection Agency Offices and the Pub that a bus crashed into, down Granby Row, on street parking is available on the left hand side of this road, and like on Store Street, sitting there waiting isn't usually too much of a problem)
If he wants somewhere to legally park and wait for you then either the Short or Long stay car parks at Piccadilly station, or the Charles Street University of Manchester Car Park is recommended for this, I won't provide any further info on this as of yet as it doesn't seem to be preferable.