What you should do to avoid razor bumps and ingrown hairs:
Clip the hairs first.
Take a warm bath or shower beforehand, smoothing the area you want to shave.
Rinse the area with cool water.
Never dry shave. Use shaving cream generously, applying it a few minutes before you start shaving. Don’t use male shaving cream (unless it is very mild and unscented), but rather buy female shaving cream.
You need a safety razor: the blades protected by steel wires to prevent cutting yourself. Making sure the razor blade is sharp enough. If it drags over your skin it certainly is time to change it.
Pull the skin straight with your free hand and don’t apply pressure shaving. When you shave your scrotum you have to realise it’s a lot of work. Start at the bottom, pulling it up. Next do the sides and do the top in the end.
You can shave in the same direction as the hair growth or against it. Shaving against the hair growth gives a closer shave, but it increases the risk of ingrown hair and skin irritation. It’s probably best to alternate. First go with the hair growth and against it when you go over it a second time.
Don’t go over the same area more than two or three times to prevent skin irritation.
Wash generously with warm water afterwards. Apply an aftercare product, like baby oil or a cream (without fragrance), to sooth the skin. You may also use this between shaves, reducing the negative effects of stubbles.
Avoid tight clothing to minimize the risk of irritation.