The freckles were done very lightly with coloured pencil. ;~)

Not sure why your rock salt hasn't worked. Maybe it needs to be relatively fresh? (I say 'relatively' because, although this was fresh out of the packet, it was from the back of the pantry and had a use-by date in the 90s! hahahahaha! I only kept it cos I knew I'd use it in my art.) I don't use it more than once.
You could try Epsom salts. I haven't used that with watercolours (yet), but I have used it successfully with silk painting. :~)
The other thing to remember when using the salt is that the paint has to be very wet other wise the salt can't push/pull it.

And for brand of watercolour- I use Windsor&Newton in the wee tubes. :~)