Plastic yellow mixing stick, as I have, should be available at any quality auto body filler material supplier. Well worth a few bucks.
With any filler can you first want to mix the whole container with a stick scrubbing the sides & bottom . This is needed mainly to not use up the ( honey) portion than separates & rises to the top. Otherwise the last portions of filler are much stiffer & less creamy. Evercoat does sell the honey additive separately which you can mix a little back into filler if needed to make it mix & spread better.
Mixing can of material too fast as well as when mixing portion with hardener definitely will add to pinholes.
Extra thickness, as Chris mentioned will definitely add pinholes, primarily because you can't use as much pressure on thicker applications to make the air bubbles pop out..
Many times I like evercoat metal glaze for final skimcoat. It's both thin & more solid at the same time as opposed to fillers in gallon containers & great for filling pinholes.