I agree, it needs to be worth your time. I just won a 25K deduction on my personal home and 10K on a rental, both in Parker Co, so it was well worth the time. Hopefully I win on two more rentals in Tarrant co later this month, one of which is my an IRA.
The best tip I can give you is, do your due diligence as you normally do, don't go overboard on your justification for the reduced value, and provide SOLID evidence to support your request.
Good luck.