Hello. I had a roof leak that softened by plaster and lathe shower
wall and bulged the wall. I removed all the tiles from the affected
area, removed the P&L and installed Durock. I'm now ready to re-tile.
I just wanted to get some advice on how to best do this. I have read
countless posts indicating that you can forget the premixed adhesives
for shower walls, so I will be using a dry modified thinset. My main
concern (other than mixing the thinset to the proper consistency) is
making sure the tiles don't slide down the wall. Maybe this won't be
an issue since they are only 4 x 4 or so but i'm not sure. since I'm
replacing tiles I really can't start at the bottom and work my way up,
it really has to be from the top down, beginning where the existing
tiles are still on the wall.

Can anyone recommend a thinset with good adhesion and/or give me some
tips to keep the tiles in place? I've already read that I should keep
my trowel lines horizontal, which makes sense. Should I be taping the
tiles to the tiles above as I work my way down?

Any advice would be appreciated. Thanks.