You can do it the way you have but the easiest is to use a reusable film canister. How ever you do it though, make sure to tell the processing people that you have done this, as if a bit of sellotape gets stuck in the processing machine it takes forever to get it out and they won't be happy. If they know they can sort it out before hand. Also best to use masking tape as it doesn't affect the machine so badly if it does come off.
Also with exposure, the cool thing with red scale is you get a result wether over or under exposed. Very underexposed is like red and black - over exposed is white and yellow. And there's loads of tones in between. Just go mad and experiment. Don't worry about getting a certain exposure as you'll still get something interesting
You can do it the way you have but the easiest is to use a reusable film canister. How ever you do it though, make sure to tell the processing people that you have done this, as if a bit of sellotape gets stuck in the processing machine it takes forever to get it out and they won't be happy. If they know they can sort it out before hand. Also best to use masking tape as it doesn't affect the machine so badly if it does come off.
Also with exposure, the cool thing with red scale is you get a result wether over or under exposed. Very underexposed is like red and black - over exposed is white and yellow. And there's loads of tones in between. Just go mad and experiment. Don't worry about getting a certain exposure as you'll still get something interesting