A typical low flow toilet flushes about 1.6 to 1.8gal these days. Normal shower heads flow at about 2gpm.
1.6/2 = 0.8min, * 60sec/min = 48 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 48 seconds, it is a net gain for water usage.