Sometimes it will be best to have your pool sand (abrasive) blasted by a contractor.
This will remove the old paint (most of it) in one go and generally leave it almost ready to paint. For Chlorinated Rubber, it’s probably the best way to get it off. Also, can prepare an epoxy coated pool quickly as well.
The sand blaster may clean up his mess, ask before you accept the quote. Costs, very from location to location, however seem to range from $1500 – 2000+.
You may need to do some prep work near tiles and outlets, as sandblaster can not go right up to them.
When considering how much new paint to use, note how rough surface is and allow a coverage rate of about 20 -25 Sq M / 5kg pack for first coat and probably 24 – 27 sq M / 5kg pack for second coat.
Better to discuss with us to be sure, before you order the your new paint.