To change the touch dwell time in Grid for iPad, you must navigate to IOS settings->accessibility-->physical and motor-->touch

Toggle on Hold Duration to increase how long the user must touch a button before it activates. Use Hold Duration to determine how long you press the screen before your touch is recognized. Increasing the hold duration time beyond 0.3 seconds will cause a circular timer to display when you touch the screen. After the timer is finished, your touch will be recognized by your device as an intentional input.

Toggle on Ignore Repeat if the AAC user is tapping on buttons multiple times, and you would like to prevent multiple selections within a given time period. Treat multiple touches as a single touch: Turn on Ignore Repeat, then tap + or - to adjust the amount of time allowed between multiple touches.

Once you have adjusted your settings to a desired calibration, toggle “Touch Accommodations” on at the top of the screen