Sealing 130 tub floor etc ?

hmmm, nope.

I would not believe the hype on any 'water based' paint that claims it can be sprayed over bare metal.

Granted, the 130 tub is aluminium, so it wont rust - however, if you want a 'proper' job, you need a primer and a paint that will chemically bond.

i.e a 2k ( 2 part) primer on first, followed by a 2k tub liner, like raptor liner for example.

Also, unless you are prepared to get 100% of the grease, dirt and grime off the surface, and key the entire surface to get a good bond, don't even bother starting, you'll be wasting your time. within months the stuff will be cracking at all seams and joints, and peeling off all the poorly prepped surfaces.