# Accessible reference for (scattering) $\Psi DO$'s on manifolds

I am currently trying to understand Hassell, Tao, and Wunsch's paper on Strichartz estimates on non-trapping asymptotically conic manifolds, however, my understanding of pseudodifferential operators on non-compact Riemannian manifolds is fairly weak.

I'm familiar with the theory of $\Psi DO$'s as presented in Abel's book Pseudo-Differential and Singular Integral Operators, which covers uniform symbol classes $S_{1,0}^m(\mathbb R^n\times\mathbb R^N)$, with a very brief excursion into $\Psi DO$'s on compact manifolds, but nothing about non-compact manifolds. The only references I can find are either very encyclopedic, such as Hörmander's books, or near undecipherable, like Melrose's notes. Are there any books or lecture notes that can provide a gentle introduction to pseudodifferential operators on manifolds without immediately pursuing the utmost generality?

I take a very brief look at the paper and I did not see $\Psi DO$ on manifold with boundary being used heavily anywhere (no conormal distribution, multiple blow-ups, heavy handed symbol estimates, etc). The gist of the paper is not the non-compact setting but dispersive PDE.