1. WorldEdit (ingame MCEdit and more) 2. WorldeditCUI (so you can see what you are doing) 2. Macros mod (so you can bind copypaste to ctrl+c & ctrl+v for example) 3. ??? 4. Profit!
In singleplayer WE requires Single Player Commands mod too. MCEdit might be faster but I don't find it very intuitive to open & close minecraft all the time and move between different programs
Thanks to Macros I also have a ton of other commands like different brushes, moving & rotating of objects, undo, redo etc. etc bound on my keyboard.
I'd participate with my cathedral but I don't want to reuse buildings.. so I'm trying to get the "2.0" version done before deadline Luckily not that much work left anymore.