drive a piece of bamboo somewhat down into the center of the pot- kind of next to the main stem. all the stems close to the center, you can tie off to the bamboo. for the ones towards the outside of the plant, you can put a few stake in the ground just outside the pot and tie them off to those bamboos.
not sure how big your plant is, but maybe next year you can put the BIG tomato cage around each plant when you start the season. the plants grow up into the cage and the cage thus helps support the side branches. you may still have to install bamboo stakes to help support it in addition to the cage.
i've been doing this for awhile and have monster plants. i put all my bamboo stakes in position at the beginning of the season so that i don't hurt the roots by doing it late in the game(as you are doing).
i always have to battle high winds and rain(late in the season), so i have learned to rig up all sorts of supports throughout the season. the key is to do it at key points and key times during the season so it's always supported in case of any unexpected winds or storms and you will have several different points that are supported.
ooooops, reread your post as i finished typing my reply and noticed that you want a low key method for ti eying the plants up.
i dunno, depending on how crazy you want to get, you can camo spray the bamboo and rope?
where i live(norcal), ppl are growing 100 MONSTER plants full sun, so we don't usually worry too much about being low key hehehe