We used a 50-watt Legend 36EXT with the following settings: 45% speed, 100% power, 300 dpi, and the Jarvis dithering pattern.
Start by inserting the rotary attachment into the laser system. Turn the system on and off and the machine will reset itself to the rotary potion.
Next, put a thin layer of masking tape around your desired engraving area. Open the file and make any modifications. Run the job at a high speed and low power - just enough to indicate on the tape where the design will be engraved.
Once you're happy with your placement, apply a thin layer of dish washing detergent to the engraving area and send the job to the laser!
When finished, wipe away the detergent and when the bottle dries, you'll have a beautiful engraving suitable for any special event.