I had my own technique to mask the activity and results. I put a washcloth folded double in my underwear when getting in bed. I was careful not to raise the covers and do any bumping. I just touched my boner real lightly and in a few minutes I would cum. The washcloth caught my cum so my underwear did not get slimy.
I would wait til every boy did what he needed to. Then when I knew they were finished I would touch my hard-on a lot with my fingertips until I came. Happy memories of my cabin full of little jackers. I can still remember all those covers wiggling and jiggling.