Your absolutely right about flushing with just water! It will make the smell better and the smoke much smoother. I flush for a week in hydro (two in soil). It is extremely important if you are a connesuier. I also take my plants down for harvest in the night cycle, but i honeatly dont know if that helps all that much.. but i like to think it does ;) lol.
No i have never crossed anything as i do not want to contaminate my grow.. hopefully one day i will have the space to, but thats just not possible for me right now. definitely sounds cool tho, i wish u luck with that. Oh and im glad u dont take that adhd "medicine" (poisin), all natural is the way to go!! Stay high bro.