It has to look as if it has been placed there, ie; stuck in a headlamp brush guard, under a tow cable, between canvas items. Tree limbs etc on the turret, try to have pointing upwards as if growing, otherwise it looks unnatural and stands out. For a model, tie it on or even glue as long as it appears temporary....and don't block hatches, periscopes, gunners view or turret movement. German tanks tended to have lots more natural shrubbery due to allied air superiority but not so much for US tanks unless they were in a static position for a while. A temporary fix to cover the white star was to place a bush or a couple small tree limbs over it....in winter, a hospital sheet or pillow case "borrowed" from a dispensary. Need depended a lot on the area and enemy threat. Hope this helps.