There are two main ways to paint models, this is painting with a brush and painting with an airbrush. Airbrush painting gives a better result, but it requires the purchase of quite expensive equipment, and this is not always available, especially for young modelers. The brush requires much less expenses, but to achieve an acceptable result, in my opinion, is more difficult. My son is very inspired to watch me paint models of ships and so I bought him a picture by numbers from
https://paintingbynumbersshop.com/collections/halloween-paint-by-numbers and he was very happy!