Spin defects in solids can be engineered as well-isolated two-level-systems with coherence that can exceed seconds, but couple weakly to other quantum systems and to electromagnetic fields. In the lab, exploring quantum optical effects in the microwave regime with spin defects requires an enhancement of the light-matter interaction; this may be achieved by coupling the spin to a low-impedance superconducting resonator. I will present two recent results involving resonator design and exploration of magnetic noise-insensitive spin defects. The first is a demonstration of the dispersive shift in frequency of a superconducting resonator conditioned on the state of a single electron spin. The second is a coherent interaction between a single magnetic-noise-insensitive electron spin transition and the field of a resonator in the so-called high cooperativity regime.