GPS manual routing

We are planning our first longer trip this summer, Fl. to Ct. I don't want to take 95 for various reasons, but plan to start out on 75, 80, 81, Etc. I have a Garmin RV GPS and have used Basecamp to create a route. I find the software awkward and difficult to use. All I really want to do is get my preferred route in and be able to figure out what time to end the day and pick a decent place to stay. Has anyone had any success with this?