If your AO generates a black stuff , it means , you don t have any uv on your objects ,
you should first learn UV mapp , how it is make , the logical is like imagine you will build the object in paper ,
first , take one object , project a planar map , to have one uv out of the shell , then cut the uv where it should be , and unfold it , layout it , sort it for this single object and repeat the action for every object , then you group all of them into one shell and sort all the uv on one single map !
here was a video i did if u want , but lot of tutorials on youtube
doing this work will be long and will make your mod stands out of the other mods .... as lot of guys are only doing a dirty automatic mapping which is not giving the quality on any textures or ao !