one separates the whites from the colored ones
so that the colored can't stain the whites,
and separately wash socks and underwears.
an underwear and a pair of socks?
This sounds gross for most
but it all depends on the one who wears them.
An underwear worn the entire day
can be washed together with shirts,
pants, short pants and others
unless it's worn during high activities like sports and exercise
where it can absorb a lot of sweat and bodily dirt
that it's recommended to be washed separately.
Same with the socks.
If they are worn for just few hours
and not during physical activities like sports and exercise,
then they can be washed together with other things
even with underwears.
If he can't tolerate such and he feels disgusted,
then it's all okay.
But he has to remember that if he owns those things
and he's the only one wearing them,
then he can wash them all together in a single basin.
the dirt and sweat belong to him so he can't readily say they're gross.