Do you mean as a picture to show the overprint?
The best way is a combination of using a scanner and some photo editing software. The one thing that helps is that overprints are usually a single, solid color, which allows you to 'erase' all of the other colors, leaving the overprint.
A Vignette.
A profile bust of Queen Victoria was pictured on the first postage stamp.
1993.
"HAWAII" overprint bills were only issued during WWII. A "D" series letter indicates this bill was printed between June 1949 and January 1953 so it couldn't be a genuine overprint. Please check again and post a new, separate question.
You can remove date stamp from image using Inpaint http://www.theinpaint.com/inpaint-how-to-remove-date-stamp-from-photo.html
One requirement is that you have to be dead. Also consider stamps.com. Anyone can upload their image to a stamp.
Scot 647 is an overprint in celebration of Hawaii's discovery. It has a good value in good condition, used being available for $4.75 and mint for $9. A dealer might pay about 25% of that if they are in really good condition.
Betsy ross
ben Franklin
Rubber stamping is taking an image that is made into rubber normally mounted on a wood block and using it to create scrapbook pages, cards and other gifts. You take the stamp and ink it and then position your stamp as you want it to appear on the paper - then you take the stamp and make contact with the paper. Pull the stamp away from the paper and your image is on the paper!
image, brand, stamp, identification, crest, emblem, insignia
Overprints are used for many purposes. They can be a precancel. They can change the value of a stamp if there is a shortage or rate change. They can be used to celebrate a special event. They are also used to validate the use of stamps from another country in the local country. The study of overprints adds a new dimension and understanding of history and time to philately.