4 Answers

Yes you can-- It's an involved process using 'porcelainized' paint. There are companies that specialize in this procedure but its really not long lasting. as any paint job, your tub MUST be totally free of any soap scum or contaminants that would keep the specialized paint from adhering to the tub surface.  Looks good at first, last about 3~5 years before you see it beginning to peel..  I had it done once years ago, I ended up buying a new tub.. Not worth the money IMO and I had it done professionally.  That was several years ago, maybe today they have a better way and materials to do the job.  There's also companies that will do it right by taking your tub to their shop and baking it on in an oven. This is probably the best way but I would only consider this on an old antique cast iron tub that has sympathetic value to you..

You can do anything . Is it recommended NO !!  Will it work No !!! Is it smart NO!!!!  But if you have a paint applicator and some paint I guess you can put it anywhere . That would be my answer.

Yes but wait until you have finished having a bath.

Let it dry thoroughly or you'll slip and fall.   ouch!  LOL (This time it means lots of luck)