I've found that, when I'm having one of those 'tone-deaf moments', that tuning by octaves helps:

Open 6th, 2nd fret 4th and open 1st
3rd fret 6th and open 3rd
Open 5th and 2nd fret 3rd
2nd fret 5th and open 2nd
Open 4th and 3rd fret 3rd
2nd fret 4th and open 1st
Open 3rd and 3rd fret 1st

Run this up and down a couple of times, and it will settle in acceptably (except with your rusty old strings, Jon! - Still, that's a banjo, and you don't tune a banjo!)...