It is not difficult to get a professional result but it does take quite some time and involves many steps.
For the purpose of example, the following information is given for virgin cow hide that has been veg tanned.
Apply water based dye colour using a sponge or cloth. Artist type brushes work well for hard to get spots. Once you have evenly applied a few coats and completely covered the leather you now leave the item to dry a little, this is important because saturated leather just can’t absorb any more of the dye carrier.
Wet leather is always darker than when dry. As the leather dries it will become lighter in colour with a dull finish.
Now you can re apply. Repeat this process using even applications until you have the desired colour, it will become darker each time but never reach the darkness of the dye itself.
We make our own polish but every day boot polish is perfect. (Kiwi) brand is economical and works very well. Use a neutral or colour. If using colour, keep it close to the colour you have used to dye with.
Apply polish in small light circles, clock and counter clock wise, then straight strokes in all directions. Stick with a small section until you have a even coat. The leather will darken because of the moisture in the polish but it soon returns to original shade. The darkening effect will help you see when you have a even application. Don’t be worried about getting a shine yet, that will come in the next stage.
Once you have completed application you can use the larger section of clean brush or a clean cloth to polish.
The rough side of your leather should be re hydrated using a leather conditioner. This is important because the leather will dry stiff after being wet. The conditioner will assist in the prevention of cracking when flexed as well as help prevent water take up on the unsealed rough side.
Now you can gently flex the leather repeatedly to loosen the fibres that are making it stiff. Start with just a slight flex and increase as you feel it starting to get easier. Be carful not to distress the leather.