Bamboo stick may be less threatening and the reptomin is a bit more noticeable and prominent. Also the stick may be longer (unless you have really long tweezers) so you don't have to get your hands in the water, which may be spooking your frog. I've always fed my frogs reptomin in this way because they will not eat it otherwise (I also have a lot of floating plants which makes it rather hard to find).
Now I've had frogs that refuse reptomin and it can take a while for them to get around to eating it. I really think you should soak some reptomin with some mysis shrimp and feed them with tweezers or a bamboo skewer and see if he takes it. I cannot see him refusing a mysis shrimp infused reptomin sticks.
Some may not agree but I think earthworms, mysis, and even the occasional cricket is good for these frogs. I know they can survive on reptomin alone but I personally feel live/wet-frozen foods really enrich their diets and make for happier frogs.