C02 question for anyone who can help!?!?!

I'm interested in exposing my plants to more C02 as I have heard it helps grow bigger buds because plants love carbon dioxide. Now a C02 pump is more than I can budget for but through my research I have seen people using dry ice and hot water every few days in their grow rooms. Has anyone done this? Is it effective? Are there other things to worry about such as humidity and pot size when it comes to bigger better buds?

Thanks I could use all the info as possible since not many people seem to have much knowledge on this everywhere else i look