I think its safe to say that most of the customs here are combinations ... using items from Brickforge and others that make accessories - but also designing by putting together the actual pieces needed for the minfigs.
Some here are 'Lego puriests' who do no modding, decals, etc. They combine and use pieces from Lego alone, while many of us do the combo.
Good luck in your adventure on learning about customizing and finding the path you like the best! Either way, there is tons to glean from here in the Armory and watching what others create!
... being customized ... by the Master ... ><>