1. Get the "over 20 years" off the top of your resume. Highlight the last 10 years of employment, and only list more on your resume if you were at the same company for longer than 10. For instance, 1997-2011 is fine. Do not truncate to 2001-2011 just to identify 10 years. However, anything further back can be summarized in an accomplishment based cover letter.
2. Do not tell an employer "I'll take anything!" Would you date someone who just wanted a date, or are you looking for a mate who is attracted to YOU? Highlight why you are a good fit for the position. Desperation is unappealing!
3. Do not considerably undersell yourself to a position. I had controllers who needed cash and wanted to temp as accounts receivable reps. If it has been years since you have done receivables, the employer knows that. Take a more general accounting based position (ie: senior accountant/accounting manager).
4. If you are told that you are overqualified for a position, ask the hiring manager why that is perceived as negative. Find out what the concerns are (since you are not being hired for the position anyway, you have nothing to lose!
5. If the manager justifies him/herself as to why you are overqualified, ask if there are any other positions open that would be a better fit for someone with your caliber of expertise! You may be pleasantly surprised as to what you find out!