Last night I got myself into an odd position with a seam (yeah, I'm leaving that one wide open). Files were no good and too rough and my fat finger wouldn't get to where I needed to sand the seam.
As I was searching my junk pile of a desk for something more appropriate, I came across my can of spray mount. Then the angels did sing
I grabbed a piece of sand paper and my dental spatula and proceeded to mount a small piece of sand paper to my spatula and Viola a mini sanding stick. It will fit into
almost any tight corner and allow fine control. switch grits is easy and if I need it to spread more filler, I just swirl it around in my turps to remove the "stick" and wipe and I am ready to go. This will work on brass tube or any shape you need to get at those impossible seams.
3d modelling is an option
a true mental excercise in frusrtation