So I've looked round old threads but since it's a common issue it gets a bit jumbled and there wasn't anything too specific to me on them that I could see.
I have an event coming up next Sunday and would like to be 100% bald downstairs, back and front. I'm gonna throw out rn that wax doesn't agree with me (many attempts, home and different salons) and leaves bumps which stay so long that stuble is back by the time it's chilled out.
My usual plan is either hair removal cream or razors. I like the cream because it's pretty quick to do but there always seems to be some left no matter how I use the cream or how long I leave it on. Razors I always seem to miss bits too and getting my butt and the back of my thighs (I'm about a size 18) properly without snagging the razor seems bloody impossible.
TLDR: How do I get a smooth hairless butt and puss without bumps, burns, cuts or any other general nastiness?
I wish I knew the answer to this. I can't figure out how anyone removes their butt hair without the help of another person!
You could always use the cream then use it again (usually the instructions say 72 hours apart but double check the cream you use) on any missed bits? At least then you wouldn't cut yourself shaving in odd positions. Although I'm sure what is left won't be noticeable, I'm sure the people at this event won't be focusing on stray hairs :)
Also, it could be worth giving this a go on irritated skin, especially if you ever give waxing another chance. I was never able to shave downstairs due to the skin irritation and ingrown hairs until I started using this, now I'm smooth and irritation free!
http://www.lovehoney.co.uk/product.cfm?p=17921
Maybe a combination of cream and razor or razor and cream would do the trick. On the other hand Desperate Dan uses a blow lamp to shave. Maybe a bit severe though. 
I do a combination of waxing and plucking . Mostly plucking as after initial removal As the hairs come back through at different rates . I still get occosinal rash or bump but mostly smooth and it looks nice it's only me can feel the bumpy bits . But first few months it did look bit of a mess but i persevered and it cleared up . I pluck any strays hairs every other day , do underneath and near bum with the use of a mirror and sit open legged on bed lol . I buy them diy wax strips that you just rub togather , but I cut them into diffrent shapes sizes etc and if I'm waxing just do small area , it's mainly just couple of bits that are hard to see for plucking that I wax . I never got one but have looked into one of them intimate area Electric shavers , can't remember the name but it is specifically for genitals and supposedly gets it as close as a wet shave . Good luck with it X