Wet hair, wet shampoo bar and create a lather(some people prefer a cotton bag to create the lather) Apply to the hair, massage, rinse, repeat. I always recommend 2 washes.
When using shampoo bars for the first time, they seem very different to the traditional shampoos that we are all used to. The lather is different as its natural and not a synthetic lather. I remember when I switched to natural shampoo made from oils and butters my hair was extra greasy for about 10 days and I didn't think they worked!
I have very fine thin hair which damages easily and it used to frizz and break with traditional shampoos so I persevered with the shampoo bar and after about 2 weeks I began to notice the change. No grease, no knots, ironically my hair does not need washing as frequently and I do not use a conditioner now either as even the ends of my hair do not dry out the same.
This process happens because our hair gets its oil from sebaceous glands that secrete oil called sebum, (our largest organ is our skin!) which keeps the hair moisturized.
Often traditional shampoos are designed to strip excess oil, which helps the hair look cleaner for longer, but what in fact happens is that our skin then goes crazy producing the oil to moisture our scalp and hair and so we find ourselves in the unenviable position of having to wash our hair more frequently to stop it getting greasy!
Avoiding flight liquid restrictions this shampoo bar makes for an ideal travel gift especially if combined with a cosmetic grade travel tin.