yes it can be done- it is not a simple process. My father was a private engineer involved in the oil industry has 26 patents to his name, and has never used an attorney. However, each one was a very lengthy process, and almost always the first application of each patent would be sent back "denied" with the patent office stating some pre-existing patent. Then my father would have to file a disagreement and point out the differences between existing patents and his new one. At which point they could approve or deny again... etc...
There were a few of his patents where the back-and-forth exchange would go on for years. It can be very discouraging to the average person. My father had sort of a leg up in the fact that since he was an engineer and a draftsman, he could easily draw up his own technical drawings, and could write a book on the designs, specs, and differences from existing designs.
It can be done, but be prepared to do your own research and spend time dealing with the red tape.