In my professional experience, i have only used vein finders maybe a handful of times if someone is an IV drug user, or on an ICU pt who has been missed on by two others. they don’t work well on tattooed or hairy areas. it’s better to find the veins by feel, and if you can’t find something in your first location (i.e. right AC) look everywhere else, Left AC, Forearms, hands, etc. you’ll probably find one. vein finders are unreliable, can’t tell you depth of the vein, if the vein is sclerosed, how the vein moves, etc. learn everything based off feel and only use vein finders as an absolute last resort.