Gday.I was  at my old C/Park that we stayed in on the same sight for 34 years last night  we still go and visit friends that are still staying in it .Well we were sitting and chatting over a beer out the front as a Prado  towing a Jayco expander pulled up level with us and the chap said g,day and sussed out the site next door prior to parking as most of us do.I noticed that he had the Clearview Mirrors .He jumps back in goes a bit further forward so as to make life easy for himself.He bungs it in reverse and then proceeds to kinda hang out the window and twist his head to full right lock and begin to make a fairly smooth effort of parking ,twice yelling to his wife if the other side was OK." Stop now" she eventually sez and he proceeds to unhitch. I said to my mate that he did a good job of parking ,however I then asked if I was missing something ? "Yeh" he sez  " he never used his mirrors once ,but nearly had half his body hanging out the window "! Still the mirrors looked very nice ! Cheers !

As you said "he began to make a smooth effort of parking".  Whatever works for him is the right way - for him.

I too have Clearviews (love them) but with our 21' + extended drawbar I can't see the end of the van in them when it is at 45º to the car so I will at times look over my shoulder.

Rather than yelling to my wife on the other side we use our phones, she rings me, then with mine on hands free we can just conversationally talk our way into a site.