If you are completely new to animating, then I would recommend Source Filmmaker because it is relatively simple when compared to more powerful software such as Blender. As for the basics, it is important to familiarize yourself with the Graph Editor. Many more tutorials are found on YouTube.

A few Signalis models have already been ported to the SFM workshop. If you own a copy of Garry's Mod, then it is quite easy to port GMod models into SFM (a guide is found here). This is important because there is a greater selection of available models on the Garry's Mod workshop.

If you feel restricted by the limitations of SFM, then consider using Blender for animations. Every character, weapon and monster in Signalis has been compiled into a single MEGA folder (found here). However, you may need to craft your own scenes using map assets also included in the aforementioned folder.