People told me to stop using the harsh acids in the toilet bowl cleaners and just use lemon juice...well I tried it last time.
After about 1/2 hour of multiple applications and letting it sit for 10 minutes or so...yes the "stache" disappeared.
"The Works" toilet bowl cleaner at any dollar store does it in minutes...it may be harsher...but the results are instant and a quick rinse and some new polish/wax can be done in a fraction of the time the lemon juice treatment.
If I had a brand new gel coat/paint, I may stick with the lemon juice...but for my old tub...the satisfaction of time and quickly applying protection won out over the juice....