We had a good experience with Rapid Visa. During this long process to get K1 visa we had many forms and many questions. Rapid Visa was not perfect but they help.
If you dont have time and you dont have someone with experience about this process I recommend Rapid Visa.
Disclaimer: The information herein is not intended as legal advice and is provided for general information only.Questions involving interpretation of specific U.S. laws should be addressed to an attorney and/or government officials.