I have an 07 and the accelerator pedal pump (I do it 5 quick presses all the way to the floor because more than 3 doesn't matter, but less than 3 will do nothing) works every time.

It's not a trick, it was purposefully engineered in on many GM platforms. Key on, engine off, doors closed, depressing the accelerator pedal (3+ quick times) causes the PPS to communicate to the PCM and upon the 3rd quick press command it to reset the CHANGE OIL message.

Why 3 complete quick presses (to the floor) you ask? A consumer may bump the accelerator pedal once or twice getting settled in/preparing to get out, but they are highly unlikely to bump the pedal 3 quick times all the way to the floor and accidentally reset the OLMS.

There are a bunch more short cuts built in, that are not shared with John Q (because people that can't change a light bulb could screw up a free lunch ) like how to clear a BCM fault with the emergency brake...... and .....

 

open hood outside...

 

I used the button press method (based on the manual) on my Alpha, it took a few tries but it finally reset. Odd thing is that it never did give any beeps. Next time. I'll try the accelerator method.