One doesn't actually form a hinge when dropping a tree. The notch is cut in one side which pre-disposes the tree to fall in that direction. When one has cut sufficiently through from the other side. the hinge is formed by the tree falling towards the space vacated by the wedge.
Removing a section of the first trunk will have a similar effect when cutting the remaining trunks. The weakness caused by the section removed will cause the cluster to fall to that side, thus forming the hinge. Everything of course is dependant on the actual circumstances. Without pictures it is well nigh impossible to give proper assistance
If you have no experience of doing this then perhaps you should start with something easier. What you wish to do really is not that complicated in the right hands.
Reading through this thread I really think you would be advised to get a third party to deal with it. The trees probably have to be taken down in sections, which is always recommended anyway.