I just use the screws that come with the devices. Unless maybe it's a 30A or 50A flush receptacle that still comes with those straight flat head screws from 1975.
Normally the only time I use alternate hardware is when I need to use an extension ring, in which case I usually use 6/32 X 1-1/2" screws.
Has your man checked out the price of screws in the last few years? They are not cheap anymore, but they are cheap crap from Taiwan and China, regardless of the name on the box.
Now, when it comes to light fixtures... sometimes that's a different story. Those "8/32" screws they come with are a loose fit even for the crappy straps that come with the fixtures. I will often use my own 8/32 X 1-1/2" screws in place of them.
