Firing a 12 guage one handed with/without a stock is quite achievable even without a pistol grip, just make sure you have grasped the stock appropriately - the recoil is obviously quite significant. The pistol-gripped variants are far more suitable for this more of operation (it's what they're designed for), and therebya lot less strain for the limper-wristed.
(why they'd be using a shotgun is beyond me, try a feather duster)
Held at arms length,arm fully extended much like a pistol (& we're back to shotguns now ladies) usually affording the best results, the most common err I saw by most when using a pistol gripped variant (usually without a folding stock) is to attempt to site along the top of the barrel, & in doing so bring the rear of the receiver into facial proximity with the inevitable result, but dentists love them.
only the sort of thing one attempts when using shot other than solids, as you tend to be more intent of actually hitting the intended target, and usually at a greater range than those encountered in CQB conditions
... I miss my 'lady'
