This is a fun question, thank you!!
(https://pbs.twimg.com/media/GR0wILUXYAA6IKM?format=jpg&name=4096x4096 armor breakdown link)

It's a solo task, but tedious. A lot of his layers are pull-over style or otherwise take little actual effort to put on- some layers are already combined (such as the various scales of his skirt) or have fairly simple clasps. Getting to the "overclothes" part of his armor is easy enough and mostly just takes the complexity of "can you put on a shirt" (which is pretty manageable even at his groggiest/most hung over), and the plate armor on his chest and hips set son fairly simply.

The five billion support straps and belts take a Little Longer! That said, his armor is built to be sturdy, serviceable, and easy. While there are a lot of belts to keep everything secure, they're simple ones, and nothing is superfluous; if he can tighten a strap or clip on a belt, then he can manage the whole process just fine on his own.

It probably takes about 10-15 minutes with most of that time being devoted to making sure that armor is correctly aligned and settled; I imagine he's gone through enough budget sets of armor that didn't quite fit that he knows by now how a small discomfort or pinch can be dangerously distracting!