Howzit, So I am going to attempt to graft an arm ...

Heyy Zimbo yes it can work doing the grafting method. It is harder because most likely if your having to attempt a graft the branch has snapped completely off. Now when trying to fix this you need to make sure where it broke does not "scab" up or else it wont heal back onto the plant. It is very tricky but can work i have done it once or twice before an i had a little spot that had "scabbed" over so i took a scalpel an made the slightest cut just to get it back open to a fresh cut make sure it is fresh like that on both spots you are trying to graft the put the branch back on an use some tape to hold it on sometimes you will have to add something to act like a splint as well. You can also look into some of the different cutting method before the graft to get more surface area touching where it will be grafted. Hopefully it will take if not and you see it drooping you can always try to save it an make it a clone Happy Growing!!!