Abstract: Experimental control over the strength and angular dependence of interactions between atoms is a key capability for advancing quantum technologies. Here, we use microwave dressing to manipulate Rydberg-Rydberg interactions in an atomic ensemble. By coupling opposite parity Rydberg states, we create eigenstates with first-order dipole-dipole interactions. We study the modification of the interactions by measuring the statistics of the light retrieved from the ensemble. Furthermore, we discuss the prospects for the nullification of the interactions and the generation of bound states. These more ambitious interaction engineering proposals require precise control over the polarization of the microwave fields, which is a challenge for many atomic physics experiments. We develop spectroscopic techniques to measure the polarization of microwave fields and utilize multiple sources with independent phase and amplitude control to generate arbitrary microwave polarizations.