Oh is that this one?
When I wake up in the morning at a quarter to 2
And I feel that I want something to do
I brush my teeth
chh chh chhh-cchhh chhh chh chh chh chhhh
lol but I could never remember the other ones so always just made them up.... but somehow 3 always wants to rhyme with pee or wee....
I had to sing this every night when I was nannying. Think 3 preschoolers in a bath together! Something that helped was prob also that I brushed them when they were in the bath so they were a bit distracted. Also I'd say "what song do you want tonight?" and I'd sing a song while brushing teeth/washing hair, provided a good distraction.
They also had electric toothbrushes (you can pick them up pretty cheap) which was a novelty factor. And also if they brushed their teeth, it actually worked better cos all you need to do is hold it still.
Another particularly good song is that one off Barney...
If all the raindrops were lemondrops and gumdrops, oh what a rain that would be
Standing outside with my mouth open wide
uh uh uhuh uhuhuh uhuhuh
Cos they could sing the uh bit which I was brushing their teeth!