A typical low flow toilet flushes about 1.5gal these days. Normal shower heads flow at about 2gpm.

1.5/2 = 0.75min, * 60sec/min = 45 seconds

Assuming that you are not effectively washing yourself while ijln the middle of waffle stomping. As long as you can waffle stomp in less than 45 seconds it is a net gain for water usage.