Is it hard to take in a shirt?

Where are you taking it ?

Not at all. I've given many a shirt a good home.

No, it's hard to take in a migrant from Honduras.

As in, an alteration?

Depends how much it needs taking in. If it is a lot you have to rip out the old seams and put it back together again.

like anything ... practice helps everything improve in time

I don't know where I would take it in, but I love to take off my shirt.

No. You just bring it inside.

on a humid day

Depends where. Flip it inside out and try to keep adjacent to the original seam.

You can cut the excess after you are content with the new fit.

Not at all. As long as you know how to do it. If you don't, it is very much harder.