Extra animations on top of retargeted character within Unreal

Hi all, I’ve been practising Unreal recently, i managed to retarget the mannequin on my custom character, added the character controls with animation montage, cache pose and layer blend following good tutorials. My question is how do i add cleanly the fixing animations on my extra bones, for instance flapping plates of an armor inside unreal ? what is the good practise ?
Thx very much in advance!