Random late-night chicken questions

1) do chickens like to be pet in certain places on their body? I have 4 hens and they let me pick them up (the sploot for me) and I never know if they’re actually enjoying the rubs I give them

2) what’s the best way to add small numbers of chickens to your flock? Husband & I have discussed adding 1-2 more & our coop & run are plenty big but tractor supply only sells chicks in 4’s. We’d prefer pullets, maybe 2 different breeds, and we live in central fl.