Pre-washing (Whether it is with ONR in a spray bottle, or APC/TFR/Snow Foam.) helps to break down and pre-encapsulate large quantities of adherent dirt that could loosen up during the manual wash process and possibly abrade the paint. Most people who are serious about detailing never let their cars get that dirty, and if they do it is by incident (I.E. Your car gets splashed with salty slush/snow, you get mud thrown up on the sides, you have construction work nearby and your car gets covered in concrete dust, etc.). I do 50+ percent of my washing with ONR, and the rest with 2BM using no pre-rinse, and on the lower panels of our MINI where they curve in (The tops are in contact with the car cover, so they don't count.) show little to no wash related marring (Nothing that a quick shifty with a mildly/non-abrasive paintwork cleanser/glaze couldn't cure.). Once you correct that damage, as long as you take even a moderate amount of care with rinseless or 2BM washing you will not incur that many swirls again. You'll want to give it a quick buzz over with LP or LPL 1-2 times a year to freshen things up, but you won't have to do major correction unless you have bodywork done, or your mechanic (If you don't do your own work.) decides to rub a shop rag across your finish.
Do not be afraid to correct your paint; just take it slowly, panel by panel (Which helps if you have health problems that may preclude you from sitting/standing in an awkward position for an extended amount of time.) and you'll be perfectly fine
. If you do your homework, your results will pay off in a BIG way, and you'll have one of the nicest XJS's around
. Those swirls are robbing your paint of a lot of gloss and clarity, and you'll be blown away by the finish once you get it even 70% corrected. You have a DA, which is an advantage that I didn't have when I first tried to undertake major correction, so it will help and save you a lot of time/energy.
If you have any questions, or need any assistance, we're here for you