This is typically the technique I use to shoot indoor images. I have a variety of flash units, ranging from small flash guns, up to larger (yet still portable) studio flash units. I will typically shoot between 5-9 exposures to capture all of the shadows and highlights, and combine those into a HDR, then use that as my base for luminosity blending with he flash exposures to get a perfectly balanced image - regardless of what other light sources are present.