So with the Ross Greene process, you would make a list of everything that seems to be an issue and then order it by priority so you can work on one (maybe two) at a time.
Everything you're not immediately working on, you can be the support/enabler, because it's temporary.
This issue about getting ready and your solution being to put his work stuff out the night before is a great example - what we so often try to do, when we see somebody struggling with something, is that we offer a solution that works for us, or what we would do in that situation, or perhaps the kind of "standard advice" that seems to work for most people. But that doesn't always work for that person, because they are not us and they have different strengths and weaknesses and blind spots and so on. We all have different strengths and weaknesses, and therefore different things getting in the way. When you have a neurodiversity issue like ADHD or ASD, then "standard advice" that works for most people, probably relies on things that are not weaknesses/blind spots (aka "lagging skills" by Ross Greene) for most people, but might be for the neurodivergent person, and this is why people with ADHD in particular often seem to be unable to follow the kinds of typical solutions to common problems.
It sounds like in this case there are actually two separate problems feeding into one:
- Difficulty leaving required time for getting ready
- Not being able to find work clothes in the mornings
And maybe even a third, struggling to connect later frustration with earlier action (though this might be more of a lagging skill).
There is a very funny article here about being late for things which he might like:
waitbutwhy.com/2015/07/why-im-always-late.html
You can help him work on the "not enough time" issue by actually suggesting he does a dry run of a typical work morning (or any going-out kind of event) - if he had to leave the house RIGHT now, what things would he need to do. (Prompt if he's forgotten anything). Get him to estimate how long each thing would take. Write it down. Then actually get him to do them all one by one, time them.
Add the times together (the estimated ones, and the real ones separately). The funny thing is that the estimated ones even by themselves often add up to more than ten minutes. And the real ones will add up to even longer. But this exercise is often quite genuinely surprising to somebody who struggles with time perception. Add an "emergency" 5 minutes and that total is his getting-ready time.
For not being able to find work clothes, forget your solution (put clothes out the night before) initially because this is something that would work for you but not necessarily for him. If you getting them ready is working for now, then that's fine, just decide whether it's sustainable. If it isn't, then it needs to be added to the list and you can problem solve for it. Problem solving means finding all the barriers and then (preferably him) coming up with solutions that work around those barriers or take them into account. So for example, it might look like washing the work clothes in their own load so that they never get mixed up with casual clothes. It might be that the work clothes and casual clothes look too similar, so might involve replacing his casual clothes with different coloured ones and avoiding the work clothing colours. Or even the opposite - buying extra sets of work clothing and wearing that every day! It might be that he doesn't have anywhere to put worn but not yet dirty clothing, or he gets undressed in the dark, so the dirty/clean/worn all get mixed up. It might be that the lighting is poor in his bedroom (maybe even because he doesn't switch on the light). It might be that he does not like hangers, and prefers to keep clothing in drawers. Or maybe drawers are too out of sight out of mind, and he needs to hang clothing on his door. The point is, he identifies the problems, and instead of saying well, that wouldn't be a problem if you just XYZ, you can add "difficulty with XYZ" to the list and solve for it separately, and/or you can work around it for now as though it is just something that will always be the case. You can do this even if it is something as obvious or silly-seeming as not turning on the light. The whole point of this is that the solution needs to work for him, so if he finds it too onerous to walk three steps and turn on the light, then work around it (or perhaps get a remote controlled light or a lamp within reach or he could use his phone torch, etc etc) - but the hardest part IME is not jumping in and rattling off all the solutions that you immediately think of, the first step is just to get him to work out all the barriers and accept them as real difficulties, even if they seem trivial.
If he is explosive, BTW, then The Explosive Child might be a better read, as it explains the "ALSUP" (Assessment of Lagging Skills and Unsolved Problems) in more detail - the unsolved problems is your "list of issues".
There is also a FB group called The B Team which is dedicated to helping you work out the process but I find they get very very technical and it can be a bit overwhelming. I do read anyway, but sometimes it makes me feel a bit stressed out!