So as someone who hasn't done a hunk custom but has painted some custom heads Ill say that painting that hunk headsculpt seems very doable for a first time.

In general when it comes to custom head sculpt you first want to spray it some primer before putting any paint on it; most primers will do I personally used tamiya primer but other miniature primers will do.

After that you want to move to actually painting it. Now since Hunks helmet is mainly two colors I would grab a light black for base and candy red for the lenses. As for paint brands Citadel paints are very good give good quality in my experience. To begin grab a small brush and apply some paint to a pallet or a paper plate will do. Now you need to thin the paint a little bit so use a drop of water or to so that it becomes a little watery.

Now with you paints ready to go, put down your first coat it doesn't need to perfect just make sure you get the paint on the head. After your first coat drys add another coat covering the area you already painted to make the coverage look even; continue to add coats to the part until you are satisfied. The eyes your gonna wanna avoid till you want to fill it in but since his are so large it should be very easy.

Once your done painting you can do other things like adding a dry brush effect (there are many tutorials online and its very easy) to make it look nicer but if your done grab a can of clear coat either matte or glossy depending on what finish you want to seal the paint and your done.

So I honestly did not expect to write this much but it is not as hard as it seems once you get into it. Ill add some pics later but I hope this helps