This thing is awesome for scrubbing the tub! Mine had so much residue and gunk caked up I thought I was going to have get it professionally cleaned but with a little bit of elbow grease and a lot of OxiClean it looks as good as new (forgot to take an after pic but you can see the difference here mid-clean)
Anyways, I highly recommend this combo! I tried baking soda/vinegar and other tub sprays before the OxiClean and the dirt wasn’t budging. This is key and will make your life easier. Sprinkle all around, be sure to wet it a little and let it sit for 15-20 minutes before scrubbing for best results!