Yes, after i returned to work i travel frequently for business without the baby.
Pumping: I still pump at the fixed regularly intervals that i would when i'm in SG; that's about 4 or 5 times / day.
Storing: I pre inform the hotel that I will be staying that i need to use their freezer facilities to freeze breast milk and they are able to accommodate.
I would provide ask them to provide me a styrofoam box or provide them my own freezer bag so that my EBM stays out of contact of whatever's that in the freezer with the EBM.
I would also bring along another spare freezer bag (fridge-to-go) or the Avent's freezer bag that came with my dual pump and additional ice packs that i would also freeze in the hotel. These are to be used for my pumps outside the hotel.
Pumping outside of the Hotel: If I have to pump outside of the hotel, i would pre-check out to see if the place have fridge facilities to store my milk. Worse case my own freezer bag can also store the EBM. Or worse worse case, if you feel you're out too long, then throw the EBM away.
Packing for the return flight: I would ask the hotel or go to a nearby ice cream place (haagan daaz usually) and ask them sell me dry ice. If you can tell them the volume you're transporting back and the duration of the flight + car journeys to the airport & from airport to your home, they can provide you an estimate amount of dry ice you need.
Checking In: I would usually store the whole pack (Freezer bag/ Styrofoam box with EBM and dry ice) into my check in luggage. If i run out of space (which i do for trips to HK, TWN & AU cuz of shopping *hehe*) i would check in separately. The check in officers would ask me what is it but so far I have never been required to provide a letter nor been stopped. (I fly via SQ and have asked them before. They have told me no need, just inform the officers if they ask)
hope this helps