You were extremely close. You will start seeing scenes of what ever you think of right when you are about to doze off and have a dream that will most likely become lucid.

That is almost exactly how it is for me.

As soon as you have some of those random thought scenes, just keep telling your self (in your head) "I am dreaming.. I am dreaming.." And you will probably fall asleep shortly after and hopefully in your dream you will realize you are dreaming.

And it sounded like you were napping. Napping is a ton easier to realize I am dreaming for me, probably because your mind has been fully awake for most / some of the day.

Just keep napping and I'm sure you will get a LD very very soon. Good luck!