Is this an absolutely necessary step? If so, how do you guys do yours?

it is said that time spent on polishing the tube is one of the best things that one can do when tuning.
it is recommended that a 400 grit polish be used on synthetic seal guns.
i use a brake cylinder hone with an extension added and i do this to every gun i tune.
i also finish the seal with 400 grit when sizing it.

Craigie...the word polish is indeed wrong...we dont polish the tube..we hone it.crosshatching enables the lube to move.keeping the seal lubed.when done right...the seal and lube make love.:)

i'm with you on that.
the boys at the GTA got me on the polishing kick.