the same tilde tweak is also in maya 2008 ext 2 otherwise jes turn on the tweak option in yer transform tools options. ( which might also be preferable to holding down the tilde when in a heavy tweak sculpt session )
for brush like behavior remember to use the b hot key to enter and set soft fall-off.
fer quick zbrush like shift-smoothing. a script would have to:
On hot key press on..
record yer current selection.On hot key release...
select yer mesh at the object level
enter the sculpt polygon tool with the smooth or relax option
restore original selection
restore the previous tool