[Unofornaio]

Great suggestion.
For those getting ready to buy a trowel this (picture) is called a margin trowel and works excellent for this type of work. These are stainless steel but Marshalltown makes very good steel ones. When buying one make sure you can see the weld ghost on the underside this is a sign of a good weld, and makes a difference in price. The others will break or bend at the attachment point after a few uses.