Panel lines are good, they're great ways of making big flattish areas more interesting. The key tools here, in Fusion360 at least, are "Split Face", "Split Body", and "Press/Pull".
Making these can be a bit of a fiddle, but there's a usually a way. I'm going to go through a basic example here to show you the two ways you can do it. We'll start with a weird starting shape:
Selecting the right plane for the initial sketch needs some thought. You're going to be projecting this sketch onto the face. The projection tends to go a bit weird on areas which are nearly perpendicular to the sketch plane, bear that in mind when you're lining things up. Here I've done a really rough sketch of the kind of shape that's quite common.
There are two ways of splitting this up. You can split the faces up or the whole body using the sketch. To split the faces, select the faces you want to put panel lines in, and hit the split face tool. Then select the sketch, you should get the big red cut showing. If it's an open sketch, you can extend it out in the sketch plane with "Extend Splitting Tool".
The important step is using press/pull, which is a shortcut to the offset face function. This offsets the faces either into or out of the starting face. It's very fussy, depending on how you've selected and split faces. Sometimes selecting extra faces (for example the underside in this case) can help.
Splitting faces is neat, but the split face/offset method can be unreliable. Split body and offset can work much better. Select the body, hit split body, select the sketch and split the body.
Then you can hit offset face and make that line.
The next step you have to do is combine the bits back up again. I usually use the main body as the target body and the little bits as the tool bodies. You want the same component, and not to keep tools (this stops cluttering things up).
This is what it ends up looking like. You can see how breaking up the big expanse of face makes even this simple part more interesting.
You can see how the left hand side has gone a bit funny because the face was perpendicular to the sketch. You can mitigate this by having a little rectangle on the sketch to make the end of the offset a bit cleaner.
So taking it to the n-th degree, this is what you can do when you use lots of this. Forming panel lines can break up large areas and get some visual interest.
