Chris,
Indentations from chair legs etc. consist of three main causes.
Pile crush.
Backing stretch.
Underlay compression.
The first can sometimes be reversed and the practise of putting an ice cube or pouring water into the dent is an attempt to cause local shrinkage to combat the stretching. Unfortunately water-shrinkable backings are also the ones that can cause cellulostic browning.
Personally, all I do is, after rinsing, use the vacuum hose-cuff to lift up the carpet out of the dent and to speed-dry the pile upright. It often helps and will sometimes remove the dent, sometimes convert it to a bump, but that's as Far as I go.