How to efficiently hotkey your units in production?

Sometimes I am fighting and producing at the same time, but I find inefficient the way I add my production units to my army hotkeys.

I usually use my select all army key, to ctrl+click the unit I produced, selecting all of the same type, then ctrl+group-number to reassemble it.

Is there any established way to do it more efficiently? I have pretty low skill but I am aiming to learn "the right way" from the start.

I think what you'd like to do is add units to an existing group. If you have your army on control group 5 for example, you can select the new units and press Shift5 to add them to that control group instead of reassigning the control group to just those units.

You can select the new units however you like to do this, but generally you will have to look at them unless you already have them assigned to a key (I'm not counting F2 for the moment). Depending on what race you play and how you like to do your production, you may find it useful to have a camera location saved where you have your production rallied so you can quickly switch there, add your units to control groups or give commands, then switch your attention elsewhere.

I'm not saying you shouldn't use F2 at all, but it is generally considered a crutch and can cause you to move units in a sloppy way. It is usually better to add units to specific groups and use either those groups or your mouse for better control. For example, attack-moving your entire army more than a short distance will usually cause groups of units to separate significantly which your opponent may take advantage of. I don't believe there's any set of methods you absolutely must use to play the game well, but if you're looking for the "established way" then I would avoid controlling your whole army with one button.

Another common technique is to use a camera hotkey to your army rally point, Ctrl + Click on unit types and assign/append them to your preferred hotkey group.

I guess it is easier as the zerg as you can assign/append the units to a control group when they're still cocoons, like you morph 8 Hydras that you assign to 1, deselect and reselect your larvas and morph 8 Roaches that you assign to 2, deselect and reselect again your larvas and morph 8 more Hydras who are going to be morphed into Lurkers later and assign them to 3, that kind of stuff.

But again, even as zerg, you can still use a camera hotkey on an army rally point.