Skeletal animation COLLADA matrix multiplication - opengl

Question

I'm trying to implement skeletal animation in a small program I'm writing. The idea is to calculate the transformation matrix on the CPU every frame by interpolating keyframe data, then feeding this data to my vertex shader which multiplies my vertices by this matrix like this:
vec4 v = animationMatrices[int(boneIndices.x)] * gl_Vertex * boneWeights.x;
Where boneWeights and boneIndices are attributes and animationMatrices is a uniform array of transformation matrices updated every frame before drawing. (The idea is to have multiple bones affecting one vertex eventually, but right now I'm testing with one bone per vertex so just taking the weight.x and indices.x is enough).
Now the problem is calculating the transformation matrix for each bone. My transformation matrix for the single joint is good, the problem is that it always takes (0,0,0) as pivot instead of the pivot. I took the joint matrices from the COLLADA which correctly shows my skeleton when I draw them like this:
public void Draw()
{
GL.PushMatrix();
drawBone(Root);
GL.PopMatrix();
}
private void drawBone(Bone b)
{
GL.PointSize(50);
GL.MultMatrix(ref b.restMatrix);
GL.Begin(BeginMode.Points);
GL.Color3((byte)0, (byte)50, (byte)0);
if (b.Name == "Blades")
{
GL.Vertex3(0, 0, 0);
}
GL.End();
foreach (Bone bc in b.Children)
{
GL.PushMatrix();
drawBone(bc);
GL.PopMatrix();
}
}
So now to calculate the actual matrix I've tried:
Matrix4 jointMatrix = b.restMatrixInv * boneTransform * b.restMatrix;
or according to the collada documentation (this doesn't really make sense to me):
Matrix4 jointMatrix = b.restMatrix * b.restMatrixInv * boneTransform;
And I know I also have to put the parent matrix in here somewhere, I'm guessing something like this:
Matrix4 jointMatrix = b.restMatrixInv * boneTransform * b.restMatrix * b.Parent.jointMatrix;
But at the moment I'm mostly just confused and any push in the right direction would help. I really need to get this order right...