This topic usually leads to
IME the paint will continue to harden for some time, so if you polish it right away expect it to be soft. As noted, it's already been washed/sanded/polished/etc. most of the time anyhow (by the shop).
Sometimes the fresh paint is *so* soft that it'll be tough to get a nice final finish, in that case just wait a while and redo it.
*I* wait at least 90 days to wax/seal (using a fresh-paint-safe glaze in the meantime), so as to avoid intefering with the outgassing, which could result in the paint not attaining its maximum potential hardness. Others believe that this waiting isn't necessary.