Tips are where you're going to make the most of your money with the job of skycap. Think about it. For the customer, it looks like you're going above and beyond the call of duty whenever you help them, even though it's simply your job. Travelers are often feel guilty for having complicated or foolish sounding requests, which means they'll tip you good for making them feel comfortable after asking, and then actually helping them.
The hourly rate won't be so good, and you will have to be great at customer service, but that's not so bad. You have to do the same thing when you work at Starbucks but the tips won't be half as good. Might as well put all that energy in a place where you could take home six figures after tips.