It's a bit tiresome repeating Ctrl+., or $\uparrow$, Shift+$\downarrow$ (in Mac), or grabbing the mouse to select the bracket every time one want to change the cell style.
As style commands on empty selections aren't even registered unless you type something following, do you Front End experts know if is there some hook, trick, option, shortcut, or configuration to effect the style application? Like this: if there's a non-empty selection, do as always; if the selection is empty, change the cell style.