I have never added C02. I have saw the DIY systems with 2 bottles. My questions is can you just put a solo cup of water inside the tent and throw in some sugar and yeast?
don't waste your time or money, if you don't use the proper equipment and maintain the proper environment, you're spinning your wheels. just provide enough fresh air.
When I got started I had my fermenting room and grow tent in the same room.
Fermenting 250L per fortnight to be stilled to 50L of 98% for running in my track car.
Made no noticeable difference compared to not doing it anymore since its cheaper to buy E98 now then make it at home.
The only real difference would of been on the fermenting side which went a bit quicker since the lights kept the room in the 28-30C range,
Ive heard those exhale bags are not worth it, but I have heard of people who home brew beer getting good results. Would have to see conclusive reviews of the bags to make me wana try them.
I did it once , and I won't do it again . To much trouble, to many ants , and just more crap in the way. I had no way to tell if it was helping, and I run a 24h vent so it was just an hopeful thought, but a waste of time.