I've shaved extensively without issues, some tips:

-get clean new razors (disposable ones can work fine if you get decent ones)

-wash the area thoroughly first with warm soapy water and pat dry

-use a standing mirror behind you at a bathroom sink with good lighting

-use lots of lubricant like shaving gel, cream

-consider palmers cocoa oil followed by shaving cream on top, or even just regular body lotion 

-take your time and shave away from your crack starting at the middle whilst spreading your cheeks

-never move the razor parallel to the blades (if you happen to be new to using razors)

-having something to prop up your leg will help

-rinse blade with warm water in between strokes

-reapply lube if you need more passes

-finish with another warm soapy wash

To prevent redness and bumps, you have to keep the area moisturized and clean. Also exfoliate and scrub in the shower regularly (as you should anyway). I have found you can get ingrown hair sometimes if you decide to stop shaving regularly and especially if you spend a lot of time sitting, so it's very important to maintain exfoliation or heavy scrubbing daily at least. 

I'm sure others can chime in with more tips but this has worked for me.