I know that not all areas are the same, and that our industry has undergone significant changes, but I believe that your time is better spent meeting, not mailing lenders.
Banks and mortgage companies get hundreds/thousands of mailings, and most wind up at the bottom of someone's drawer.
Going through all the paperwork necessary to be placed on an approved appraiser list is nice, but being on the list does not mean that they will call you.
In my experience, the people who place the orders call either (1) appraisers they know and are comfortable with, or (2) appraisers their Boss tells them to call.
Believe it or not, my experience has shown that instead of spending eight hours filling out forms, spend those eight hours trying to meet one or two people face to face. Leads? Ask local realtors which lenders they use and ask for a NAME. Call that person, ask Who is the person who is in charge of placing/directing orders. Then try to get a meeting with THAT person.
Alternately, join Rotary, call any Lawyer friends, anyone who has a friend at a bank or mortgage company, and work on those names first. A good introduction or reference is worth twenty approved lists.