So besides the griots mop stick, let's get back to the Boar's Hair brush, Any one have feedback?
Here's my take on this. I do not wash/detail for a living, just my vehicles and some friends/family, so take my comment with a grain of salt.
I bought the Montana Brush many years ago from AG to use on my Yukon. It was a work DD and white and the paint was reasonably hard. If I was super gentle it did not appear to swirl much. The paint was well maintained but my goal was to get a large vehicle washed as quickly as possible with minimal damage.
I tried using it on darker colored sedans and I did notice it marred it up a bit. Some of the panels were resprays so I'm sure the paint was softer.
I have a 2014 Jeep Grand Cherokee in dark metallic gray. It is my business vehicle and while it looks pristine to others, my main goal is to keep it looking good with minimal effort. I use the brush often with no markings at all. However, the paint is very hard and since it has metallic in it I suppose it masks any micro marring.
If I was starting over I would probably get the Griot's MF mop head since it's most likely safer. However, I have never used it so I can't comment first hand.
What city do you live in? Maybe someone on this forum that lives near you could let you try their's to see how it works. If you lived in AZ I'd gladly let you try mine out.
Good luck on your decision.