Quoted from Blackbeard:For whatever it's worth, many pin owners can't/won't send out a pf for a clear coat because they don't have the ability or desire to unpopulate the pf.
I'm in that grouping and it's for lack of confidence in taking apart the pf.
I am in the process of finishing a brush coating on a Fireball II playfield.
Hindsight is an unkind mistress LOL
I did not know what I did not know. Last June I started a playfield swap, took me about six weeks to get everything moved over, got it up and running and playing but realized then that I probably should have cleared it first.
I'm new to this stuff. Seems like instead of trouble-shooting little things, I dive right into the hard stuff. 
So, since I didn't want to de-populate the PF, I decided to use the KBS stuff and brush it on. It turned out pretty well, and the field is protected (it had some planking) and it shines real pretty. I just finished the cutting polish, and am working on the final polish before letting it sit for a week or two before waxing.
This game is a restore, I am not worried about value per se, because I'm keeping it to pass on to my kids or grand-kids one day, but I made some mistakes, mostly in the leveling of the clear.
Everybody here that has recommended spraying is spot on correct, but these fields can be brushed with minimal PF de-population, while still "in" the machine. It's much harder and perfect results may not be achieved like a spray clear, but it can be done.
And as some others have pointed out, when it comes to clear-coating a playfield, less is more. That was my biggest mistake (and I didn't even use a lot), but I didn't know what I didn't know as it pertains to brushing on a clear-coat.
This playfield had some weird risings around the Fireball Bonus section, that perfectly reflected the inserts. There was some of that up top coming off of the sploosh waves that are around the pop bumpers, and they ran out to the side. Some of the irregularities with how the clear settled may be tied to that and the minor planking that existed.
I will try to post some pictures soon. I shot some yesterday, but I am not happy with how they turned out. I may get the tripod out and take some formals. And I am not worried about criticism.
Test rolled the ball down and across the field yesterday and the ball seems to roll fine, even across the inserts.
But, in the way of being repetitive, those who suggest clear-coating by spraying, are absolutely correct. But there is hope for those of us who don't want to completely depopulate a playfield.
Just be careful, and remember these friendly unsolicited words of advice: I am my own warranty station 