I followed #536 and my custom armor is now mostly rendering in 3D with EpicFightMod.
However, there are still some glitches when rendering. I do not want to spend too much time on this (and you probably neither), but maybe you can have a quick look at the code. Maybe there is some obvious fix.

Without EpicFight:

With EpicFight:

Code for boots: https://github.com/TeamLapen/Vampirism/blob/741f62a7174efac9ce57403caeea41dcc3c8530f/src/main/java/de/teamlapen/vampirism/client/model/armor/ClothingBootsModel.java
Parent class: https://github.com/TeamLapen/Vampirism/blob/741f62a7174efac9ce57403caeea41dcc3c8530f/src/main/java/de/teamlapen/vampirism/client/model/armor/VampirismArmorModel.java

(Currently there is no release version which includes the code above (with the correct model hierarchy), but I could provide you with one or you clone/build it yourself, if needed.