Hello I'm not to sure on some classes but ill give it my best shot.
Class 158
pre covid these normally only got to London on peak time trains and their associated workings with the rest of the time this being 3 units on Romsey-Salisbury via Southampton workings.
159's only do Waterloo to Exeter and Bristol, however I think a large number of these are either fast Basingstoke to Waterloo or only stop at Clapham or Woking.
GWR 165's not sure only ones that I know will be 165's are the branch lines with majority if not all other Thames Valley working class 387's. Chiltern I have no idea sorry.
1711's last I heard they were staying until a replacement or battery elecrostars could be successfully trialled. See this thread for more information
https://www.railforums.co.uk/threads/battery-powered-electrostars-for-southern.192809/
315 and 317's scrapping has already started so you may never be able to complete them as a number are already stored.
319's no idea
321's Liv street to Stratford seem to be a good option for those.
350's are good for Harrow to Euston as well as Watford however am not sure about Oyster as I think it has its own fares and that travelcards do not apply to Watford Junction.
375, 376, 465, 466
All gettable on Cannon Street and Charring Cross to London Bridge moves as well as a number of Victoria to Bromley South moves.
377/1 and /4's
Main work is long distance I.e Vic- Southampton, Brighton, Portsmouth and Eastbourne all of which call at CLJ and East Croydon
387
Normally Vic to Gatwick fast and Vic to Brighton via Gatwick so no calling in the zones.
455 and 456's
Do what they have done since they were introduced so a while of Vic and Waterloo to Clapham moves will get you a large number.
In terms of breaking it up all I can suggest is aim to focus upon different classes for a couple of days at a time. obviously primarily the at risk classes and try to go for different areas even with the same classes, for example a few hours on Waterloo to Clapham then move onto Victoria to Bromley South via Victoria and may as well do the branch.