I disagree with the prior answers as that is what the assessors want you to do.... go it alone..... so you are stuck with there results if they disagree. As a state licensed appraiser also I have provided the requirements to assist in getting your tax bill reduced for many clients and sending a report attached certified to the assessors with provided information does in fact get thre attention.
I have done property reassessments for clients and suggest submitting an appraisal along with the required form to the assessors office. I also send it certified which puts them on notice you mean business and you have proven your case. I am a state licensed appraiser and we have done this before, but its up to you to prove, not the assessors. Most people give up and don't take this seriously, which is what they hope most people do. Feel free to call or email me your address and I will let you know what I see the taxes should be and what I could provide.