Dead Eye problems post oil wagon train heist (PC)

[MalloyAT]

Howdy y'all,

Been playing a few days, taking my time and enjoying the game alot!
 

Until now I've been exploring alot, only moving the story ahead when out of other quests, this time though I experienced a problem and now I'm lost and not doing a very good job in the game.

I've just advanced the storyline past the train robbery involving the oil tank, and Dead Eye just got better... that is, for me it's really bad because I cant figure out how it's working anymore.

Before this point in the story I would go into Dead Eye mode and just tag a load of targets by passing the crosshair across different targets, but now the 'upgrade' I'm being told that I can paint targets at will.

Now, I have no idea of how to do this, now I enter Dead Eye, target one target and shoot leaving Dead Eye mode... What am I doing wrong, am I missing out on a key to 'tag' targets manually while in Dead Eye mode, and if that is the case, what is the key? If this is indeed the 'improved' version of Dead Eye (being able to only hit one target at a time) can I revert back to the old, but wastly superior version, of Dead Eye?

Thanks in advance :)

[Doc101]

The key is listed as "Dead eye tag enemies" under "Combat, lock-on and interact".