How do I apply this at home, and is the 4 ml + 1.5 g kit enough for both brows and lashes?

This is a one-application kit — the 4 ml of colour cream and 1.5 g of developer are sized for a single tinting session rather than a multi-use tube, so one pack typically covers doing both brows and lashes in one sitting. Follow the exact mixing ratio, timing and application steps in the enclosed instructions; the points below are general practice for using a kit like this well.

• Prepare only when ready to use. The mixture must be prepared fresh, because the colour reaction starts as soon as the two parts are combined. Mix it right before application and discard any leftover — it will not keep for a second session.
• Start with clean, dry hairs. Remove all makeup, skincare and oil from the brows and lashes first; residue creates a barrier and leads to patchy colour.
• Protect the surrounding skin. A thin line of a rich, plain cream (such as a barrier or nourishing cream) applied around the brows — carefully avoiding the hairs themselves — helps prevent the dye from staining the skin beyond the shape you want.
• Work precisely on lashes. Keep eyes closed during lash application and processing, apply only to the hairs, and never let the mixture contact the inside of the eyelid or the eye itself.
• Rinse thoroughly. After the instructed time, remove the dye with a damp cotton pad and rinse until the water runs clear.

Remember that the 48-hour patch test needs to be completed before the session, so plan the timing accordingly — for example, test two days before an event, not the same morning.