Teaching Rayyan to dress up on his own is pretty tricky and not really easy. What we do is that we get him to use a stool to help him to wear his briefs and pants. That, he can pretty much do on his own, although I must add that he needs a lot of encouragement and motivation because he gets frustrated easily. Also, he tends to lose focus easily, looking everywhere but not at the piece of material in his hand!
Putting on his t-shirts is harder though. He still need help with that. Hopefully he will master that skill soon :)