Holstering a pistol equipped with a red dot sight is one of the hows that accompanies the whats and whys of carrying a handgun/red dot sight combo. Particularly if there is also a weapon light aboard. Here's one option that features and Aimpoint ACRO and the Surefire X300U (though it would work one other optics too).
What does it mean to "go heeled"? The expression "going heeled" is Old West/frontier slang for carrying one or more guns. There's more to carrying a gun than carrying a gun, though.