I think sometimes we get caught up in complex drills. They're important, sure, but we also need to keep our basic look-and-shoot skills sharp as well.  For example, I knew an instructor (a SWAT and DEA instructor) who taught all kinds of combat firearm classes, the kind where they roll on the ground so much you can't tell what color clothes they're wearing afterwards.  But also, every morning, without fail, he did 50-100 simple fast draw-and-fires (dry firing, of course), right there in his bedroom. Needless to say, he was pretty slick drawing and firing that SIG P226.  

You can do the same with your AR.  Just stick a 1-inch colored dot on a wall, down at one end of a room or hallway in your house.  Then, as far away as you can, step out with your AR, drop to one knee, capture the dot in your sight and dry fire at it.  You don't even have to dry fire, you can just press on the trigger.  Do this from different directions as well: to your left, your right, and behind and in front of you.  Yes, it's good to know how to fire left handed while running backward blindfolded, but it's important to get these basics down, too.  You'll be surprised how much your target acquisition speed will improve with this kind of basic daily practice.

I try to do the same at home in the garage or basement.
A simple chair or old night stand can be use as a "barrier" to step out or lean out

I've always been hesitant about dry firing without pressing the trigger. Muscle memory can work against you at  the time of need.

I get what you mean there.  You're trying to build good muscle memory, not reinforce bad habits.  I tend to dry fire the first "shot" and press the trigger down on the second "shot" while dry firing, but in both cases, I try to apply the correct pressure.  The OP might have meant that in his post.

I am a huge fan of dry fire practice to augment live fire.  No matter what shooting sport I've played, it has really helped me with building that muscle memory.

What are you training for?

If to learn your trigger, then go ahead and press the trigger on a cocked hammer.  Learn how much creep it has, where the release point is, maybe even where the reset point is. This should take you 50-100 reps to train yourself to know that trigger.

If to learn correct stance, rifle mount, cheek weld, sight alignment, sight picture, use of cover, etc., don't worry too much about pressing the trigger in dry fire. You are grooving in neural pathways for your body and arms to automatically perform those actions quickly and correctly. Interrupting that practice to run the charging handle so you can get more trigger pulling reps is teaching your body to perform things that you don't want it to do.

You can get 100 reps of getting into position, mounting the gun and  aiming in in the same time that you could to 15 reps doing the same thing with cocking the hammer.

If you want to practice malf clearing, set up some malfs and practice real, complete clearing drills, not just running the charging handle.

My 2 cents.

Gringop