Grouting a small hole with a spatula and putty is quite simple. Just fill the hole well after removing the dowel (if present) by pulling it out with a pliers or pushing it into the wall using a screwdriver.
But it may happen that large holes are formed and in this case the affair is little complicated.
In fact, it will be necessary, before grouting, to insert a small ball of very compressed paper and then stucco.
In any case with dry putty or after a few hours it will be good to level the stucco with a fine glazed carat.
There are commercially available pre-mixed fillers (French filler) or powder that must be prepared by kneading them with water.
In this last case the advantage is that they will not dry up and will be preserved over time.