how to build a shieldmarshal...

[Obsidian]

Seriously, what is the best way to do this? Straight gunslinger or urban ranger, or Trench gunner.

I was thinking: infiltrator inquisitor(black powder inquisition)1/urban ranger 4

[XMorsX]

I would probably go for Musket Master 5.

If Trench Fighter is allowed, definately grab the opportunity to add ex to damage and get lots of bonus feats with only 3 lvls of fighter. My issue is that in order ot have it allowed, you should play a guns everywhere campaign, in which the Gunslinger has Dex to damage by lvl 1. But if you can convince your GM to allow it in a normal setting, Musket Master 1 / Trench Fighter 4 makes for a great start.

[Lamontius]

There's always the Shield Marshal prestige class, from Paths of Prestige...also, didn't Faiths of Balance introduce a bunch of new gunslingery law kinda stuff?

[Rynjin]

Yeah, I'd go something like Gunslinger 5/Shieldmarshal X/Inquisitor Y.