What I suggest is to start with slow periods like 10 minutes at a time and give treats while they have their outfit on to associate good things with getting dressed.
Also to start make sure that the outfit is roomy and soft, a good first item to wear might be a loose, soft tee shirt or tank top.
I know mine are fine with being dressed now, but they still have items they dislike. I can put anything on McKenzie and she's good to go, but Emma hates pjs and refuses to wear them so we don't do those on her, and my lhasa Lula just hates all clothes so in the winter she gets a hoodie, but other than that she stays all natural
.