I agree with Wayne (usually do). Why bother cleaning the bucket? It's just going to get dirty again!

It's all sanitary in there if you followed good homebrewing practices.
I recently brewed a Pils (1.052), then a Bock (1.072) and then brewed a Rauchbier (1.054) in succession on the same yeast cake. Since the Rauchbier was only 5 gallons, I cleaned one of the buckets and used the yeast from the other. It fermented very nicely. I now believe that you can go 1.072 and then back down but just don't go up from the 1.072 for a real healthy ferment. I figured I just let my yeast have a nice 1.054 break before doing a dopplebock. I suspect pitching at a nice high rate really helped things out. I also always oxygenate real well.