Safety wise, you should stand to the side of your horse to ensure that you won't get kicked quite as easy - don't forget that it's not impossible to get kicked standing at the side either - Horses have amazing aim.
If your horse is good with picking up his hind legs, he shouldn't have much of a problem with you brushing his tail out.
I sometimes forget to practice my saftey rules as I know my horses os well. I like to stratch my horses's butt so when I'm behind them and they get touched, they think it's a scratch, so even my three months old are fine with someone standing behind them and have never had one offer to kick.
Do you have anyone avialable with horse experiance who could help you get the hang of general horse handling?
There really is so much to know, and it's a whole lot easier (and safer) if there's someon knowledgable to give you hand.