What to do with ugly tub

[Brian Pleshek]

So, I'm finishing up my rehab on my auction rental and in the basement I have a dark gray plastic shower insert.  It's ugly.  It looks rough and soap scummy and ....  So my step-mother thinks that it is as clean as it's going to get and that what remains are likely unremovable stains.  So I am wondering, short of ripping it out and putting in a new insert, are there some enamel paints or other coatings that I can apply that are "good enough"?

I saw a few articles on it like this one. But there wasn't a recommended product.  Can anyone recommend a product?  Should I get a spray on?  A roll on?  Obviously special care would need to be taken around the drain, but are there any other concerns I should have?  Is this best left to a "glazing" company?

Any direction would be helpful.  Thanks,

Brian