There is a difference between polishing and cleaning.
Most pins just need a very good cleaning.
Polishing is a bit dangerous, in that you are removing layers of clearcoat
that protects the paint itself. Buff too deep, and the paint will easily
be whipped off the field.
Many things cant even be buffed out... such as deep scratches, pits, cracks. Only way to get somewhere with these is a harsh cleaner such as
using a 'Magic Eraser' whetted with rubbing alcohol. The pits would need
to be cleared over - else dirt would just seep back into them again.
As for wax... Ive stopped using it on pins.
Wax isnt really very protective to a hyper speed spinning ball of
destruction. The wax simply parts ways - absorbs dirt and metal chips,
breaks up and dirties the entire field, subways, assemblies...etc.
At the Arcade I used to manage... I decided to try something else:
Armor-all. The stuff contains the same material they use on rollercoaster
wheels. The shine is Incredible... and the ball glides twice as fast over
it.
Less friction = less change of ball digging into the field. Also, because
the stuff is thinner and does not trap dirt inside of it... the ball will not
be pushing particles deep into the field. There is no blackened dirty
wax all over the pretty plastic bumper-towers to clean. No dirty wax
fragments in assemblies. No wax dust from dried and aged wax.
I used to have to clean the machine every 2 days or it would look so
dirty that you would have thought it was over 2 yrs without a cleaning.
The pin "No Fear", was played very frequently all throughout the day
from customers, to arcade employees.
After using the Armourall (actually, it was 2001 protectant, which includes
UV blockers

), I could let the machine go an entire week or more
without haveing to clean it... and even then, it still looked and played great. It was Amazing.
I used this method for almost a year, and there was no Ill effects seen.
The game played lightning fast all the time, had a high gloss look,
... and it was far less of a headache when it was cleaning time again.
I highly recommend this option over waxing.
* Edit
I will add, that IF your playfield is covered with Mylar... then polishing is
not such a risky / dangerous option. In fact, if can be beneficial. The
thickness and durability of mylar is much greater than that of the light
clearcoat that covers the paint on non-mylared areas.