It is true that cleaning a tub is very important before you start the preperation process. However abrasive cleasners do not clean the tub properly. Most tubs you encounter are worn out and porous. Bar soap residue (grease) and oils from bath products are not removed completely from the tub by scrubbing (Plus this must take alot of time and energy). It is better to use a cleaner that actually works like a degreaser to deep clean the porcelain. For example, Home Depot carries a cleaner by ZEP called Shower, Tub and Tile cleaner. You can wipe or spray this product on the tub. The key is to let it sit about 5 minutes, it will do the majority of the work as it disolves the soap scum. Now go over the tub with a scrub pad ( you will be surprised how little effort this takes) and rinse with cold water. I like to take a piece of wet/dry sandpaper (120 grit) at this point to remove paint spots or severe calcium stains and then dry the tub before etching. Now the acid can really do its job. Most of my customers think that I am done with the job when they walk in the bathroom after I have cleaned the tub.
