Here is the best way to clean your tub and shower inexpensively and quickly.  There is no scrubbing required, just a little patience.  First, get a spray bottle.  Zep is the best spray bottle we have purchased through the years and use them exclusively.  You can find them at Home Depot or Lowe’s.  In the following order, add 1/3 water, 1/3 white vinegar and 1/3 Dawn dish detergent.  Spray your tub or shower completely with the solution.  Let it sit for 20-30 minutes and simply wipe out with a wet cleaning towel.  For really bad soap scum that has not been cleaned frequently, you may need to do the process twice.  Depending on the level of soap scum you may need to add more Dawn.  We also use this solution for cleaning sinks, countertops and toilets as well.  This is the best process we have found for bathroom cleaning.