Sorry for the late response!
I'm aliiiiiiiiiive~! Mwahahahaha! =w=this is my first time getting on since I last posted, so this will be super duper interestiiiiiing....My more recent voxel models have been created in Qubicle, a professional program that allows for manipulation of individual parts and such.... However, I started out by using Magickavoxel! Magickavoxel is a free piece of software that allows simple editing of a single voxel model. (A link can be found here!) Magicavoxel usually won't be able to produce a polished model well on its own, though. To that end, I use Blender, a piece of free 3D modelling software (Available here!) Blender can be super duper intimidating to work with at first, but it is an extremely popular application, and many tutorials can be found for it on Youtube and the like. You can export pieces of your model one at a time from Magickavoxel into blender, and then manipulate or resize them independently.
Best of luck with all of your modelling efforts~!
(A little tip for creating models: try to keep an eye on the original style if you create fan-models for Clone Drone. Many people create voxel models that are round, large, and curvy, but Doborog has opted for a very angular, simple style. If you keep that in mind, I'm sure you'll be creating amazing fan models in no tiiime~!)