DUS - Holiday Inn: You can take a S-Bahn from the local train station under the terminal to Dusseldorf - Derendorf in about five minutes. The hotel is around 500 meters from the station, so you can decide between walking or a short cab ride.

Holiday Inn - Cologne Messe: Two choices. The S6 S-Bahn takes you directly from Derendorf station to Cologne Messe/Deutz in about an hour according to schedule. Or you can take a S-Bahn from Derendorf to Dusseldorf main station and switch to a RE (Regional Express) train towards Cologne. All RE trains stop at Cologne Messe/Deutz and using them the total time is about 40 minutes.

When coming from Dusseldorf the huge Messe halls are to the right side of Cologne Messe/Deutz station. One simply cannot miss them.

The main differencebetween the two train types is comfort, the RE trains have restrooms and a 1st class that is normally much emptier and does not cost substantially more. S-Bahn trains are typical urban commuter trains resembling subway carriages.