How to copy weights from one bone to another? I was manually weight painting some bones on one side of a character, I then named them properly using ".L" for left side and then I used symmetry to copy them to the right side.

It copied them, along with the constraints, but not the weights. How can I copy them across?
Nevermind, I'm silly. 

The way to copy bone weights to other bones is by making a copy of a vertex group that belongs to the bone you wish to mirror. Let's say "Hand.L" and then clicking on the black arrow in the vertex group panel and selecting "Mirror Vertex Group", then change the name to "Hand.R" and if you now move that bone that is "Hand.R" it will deform the mesh just like on the left side.