Use a computer to implement and check solutions to classical paradigm-based phonology problems.
From the website referenced below:
Phonology Pad is a program written for use in Linguistics 120A, "Phonology I", in the Department of Linguistics at UCLA.
PhonologyPad is a program that lets you do classical phonology problems (with paradigms, underlying forms, and ordered rules). It never tells you the answer to a problem, but it always checks your answer for accuracy, and it often points out problems with your answer that need to be fixed.