There are several key things to help in getting tight spun bugs.

I have found that you need good quality deer belly hair for spun bugs. Then you need a good thread like the Orvis Salt/Bass Size G thread or Gudebrod 3/0.

You have to get or make a good packer tool, I have made mine from a hardwood dowel. just before packing, use a small drop of super glue on the thread wrap and then pack tight. Then add another drop down in the pack. I use a long needle head cement bottle to put the glue down in the packed hair.

I have put as many as 12 pencil diameter bundles of hair on a hook. Then trim it with and old style razor that you break in half. cup the razor and trim from head to tail.

Hope this helps