Looking for advice and opinions on learning navigation skills

I fly in a moderately difficult area with lots of landmarks, lots of woods and eastern USA scale hills and mountains and very few spots to land out. Flying into valleys and not having enough space to turn around is a possibility.

To date, I've relied on eyeballing the glide path to the airport and getting back close to the pattern with plenty of altitude to spare. I'm a navigational newbie.

I've just started getting into the approach of calculating in advance "safe altitudes" at landmarks; altitudes that guarantee a glide to the pattern at best L/D with a large safety margin. My plan is to study the chart and topo maps in advance, make a list of safe altitudes and landmarks (maybe on a 3X5 card) then practice picking out landmarks and observing altitude. Plan and execute some mini-tasks around the airport with altitude targets. I'm using one of the classic books that talks about how to do this. In short, develop navigational skills without a digital PNA. Once I have better "navigational sense" I will learn to use a PNA. I'll stand off or stay well above any valleys where I might have trouble turning around.

As I get into this and realize the difficulty and complexity of navigating on paper, I'm wondering whether my traditional paper-based approach is dumb.. Would it make more sense to start using a PNA sooner rather than later? I'm not suggesting that I rely blindly on the PNA, more like a combination of traditional methods with the PNA.

Is it smart or dumb to delay using a PNA for a season?

Are there any books that teach navigation with a combination PNA and paper based approach?