I would use the ResourcePage code example to replicate the hasmanyfilemanager functionality. Also, it's not documented yet, but the AssetManager field will allow you to attach file objects directly to a page without having to wrap them in a dataobject, like FileDataObjectManager requires. I prefer the latter because I often want other attributes on my files, but AssetManager is as easy as:

new AssetManager($this,'MyFiles','MyFileClass');

ImageAssetManager works the same.