You don't need steady hands - I mean it helps - you put down a layer of wash - games workshop has a decent range - it gets into the lines and detail and then you clean it up with a cotton bud and some isopropyl alcohol.
To build confidence try it out on a tf you don't mind screwing upe.g. a ko from a dollar store.
There's also a metric butt load of weathering and panel lining tutorials on YouTube
Also ask to join the Action Figure Customs Australia group on Facebook! Expand your circle of customising friends![]()