I normally start low and work my way up. You may want to do this in a few days work rather than all at once...if the gout starts to get too stiff its hard to keep up. For baths I try to do about 50 to 60 sq feet at a time
The order does not really matter all that much really. Personally I like to work opposite from what KMS does, from the top down. My reasoning is that any grout I may drop on the floor does not have any affect on any grout already installed in the floor (since there is none). Plus I just want to avoid standing on a freshly grouted floor.
I grout the pan floor & curb then the walls. When you miv your grout they tell you to wait 15 minutes and then remix. This is because the grout starts to get hard if you don't. I mix once grout the shower pan floor while my grout is runny. Then when my grout starts to harden I remix & grout the walls. This enables grout to flow into all of the shower floor voids while still avoiding overwatering the grout. Grout is harder like cement, when mixed drier. http://www.cwremodelcontractor.com
Thanks for all the good advice. I bought an additive to use in place of water for the grout. I was told by the store clerk that the pot life is the same if just water is used. Is he right?
I have only used the add mix a few times..have not noticed much difference one way or the other.