once gassed out I'll use ZAP on the seam spray the hardener dries in a few seconds then sand away... You may have to repeat it until you've got a good build up and sand away. I use the regular glue in the beginning so the plastic bonds together.
Once you sand to your liking primer it now you can see your work. If you need more fill just put another bead and with a (anything) use the edge to run across the seam spray or put a drop of hardener. That should give you enough to do your finish sanding. If you do have a little area to tweak just apply a little automotive spot putty as a skin coat and just sand down to desired taste.
How about this Scott, It's really late but I have to do some of what I've described tomorrow and I'll post it. I have a few things to do tomorrow so it won't be until late afternoon.