Hello,
Yes I know what you mean about #7 looking great but not lasting long, but it goes on easy and fast.
Polish cleans the paint nicely but leaves no protection. Good wax protects against harmful ultraviolet rays, bugs, tree saps, and scratching.
A well waxed car should wash up nicely with cold water and no detergent. Hot water sofens the paint and wax causing scratches during washings. Detergents strip the protective wax.
I hand wash my SL with a wool mitt, cold water and with no detergent. Not possible for everyone, I am sure, but makes your paint and wax last a long time.
Joe Alexander
Blacklick, Ohio