They are a comfortable, economical, and hassle-free way of getting to your accommodation if available.
The bus stops at the Kansai airport is located here.
Where you can get to from the Osaka (KIX) Airport
With KATE, You can look up routes, stops, bus schedule, and even pick-up and drop off points before landing, but not all companies offer that so please double check.
For certain (popular or remote) areas, advance reservation for the way back to the airport is needed.
Each Limo Bus company offers different information, so look into the ones specific to your trip.