Cast Iron Enamel Bath
 

Does anyone have experience of re-surfacing a cast iron bath?
The enamel has deteriorated and is matt and rough below the water line -
about one third of the way up, and worn away round the plug hole.
I've come across a product called Tubby Bath Paint - can anyone recommend?
Also, what is the best way to level off the 2 surfaces? - there's a ridge
now where the enamel is worn away and the intact glossy surface. Is sanding
an option? or better to one-coat the lower surface to bring it up then one
all-over coat.
tia
Hugh