Rich is having trouble entering his password on his cellphone screen due to his Parkinson's disease. Leo says that there are plenty of accessibility options including the swiping keyboard. It would let him draw a line from key to key. It may be easier to do that than tapping the keyboard. Leo recommends using the Google Keyboard, GBoard.
Another option is voice dictation. Or he could use a PIN, a 4 digit number, so he could use the keypad and not the keyboard. Leo also recommends using a password manager like LastPass. That will help enter passwords automatically, and he'll just need to remember his LastPass password.