You can select just the bones that intersect the mesh in the weights panel by holding ctrl, and then press auto to calculate the weights just for them, then add the missing bones that are outside manually (perhaps using the brush mode and painting the weights, or the direct mode but selecting several vertices at once, both methods make weighting much faster!)
Another tip to weight faster is to give each area 100% of a bone, then box select the vertices in the middle and press the smooth button so that Spine will smooth them out for you.
If a process is cumbersome and auto can solve it, then perhaps you could also reduce the number of vertices you use in a mesh.
Another interesting usage tip is to start with roughly half the vertices you need, weight them, then go back to edit mode to add the missing vertices: Spine will automatically weight the new vertices according to the surrounding vertices!
Weights - Spine User Guide
