In the case of a real aircraft, viewed from a few feet away, panel lines are virtually invisible. As you look at a model from a nominal distance, panel lines would be the same, pretty much unseen. To make panel lines really stand out, I think would be inconsistent with scale appearance.
Paint sprayed at proper thinning ratio really doesn't conceal much, in the way of finer details. I'd recommend you just try painting the model and see if you like the results. I only scribe if panel lines don't line up, from one side to the other.
I have several scribing tools, of them I consider the UMM the most useable and effective.
Patrick