[JohnKSa]

Most people who I teach cannot draw their concealed weapon with one hand when it is under an un-tucked shirt, forget about a tucked in shirt. They have learned to lift the shirt with one hand ad draw the weapon with the other. But what if you can't do that?

I agree that anyone who carries a firearm needs to have a plan to not only access their gun one-handed (dealing with concealment if necessary) but also to access it weak-handed. The idea that one will always have two hands available for a draw, or even always have their strong hand available for a draw is overly optimistic, IMO.

I generally wear a Tee shirt so I practice lifting that with my thumb.
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In the times I wear a button up shirt I have no problem ripping that shirt to get to the gun.

I'm not that versatile. I draw the same whether I'm wearing a T, Polo or button front shirt. Maybe if I had a lot more time to practice I could get good enough to rapidly figure out which shirt I'm wearing and which draw to use for that shirt. As it is, I have one draw from concealment and it's designed so I can use it no matter what I'm wearing.

How about an open shirt or jacket that provides suitable concealment, but can be brushed back out of the way with the gun hand?

If you can make it work for you under the conditions you carry, then go for it.

I've never been able to make it work for me except with a jacket heavy enough that the wind won't blow it open. Otherwise, if I can brush it back away from the gun, the wind can blow it back away from the gun too.