Anyone have damage from blow-only winterizing?

I have done blow-only winterizing a few times on two different RVs and have not had damage. Our previous small MH had pairs of drain valves in two separate parts of the house, so I felt confident about that one. This one does not, so I'm not feeling so confident. I am going to use pink stuff in it.

I also wonder if I am introducing any oil from the compressor into the lines. I have a couple of little oil-less units, but I am not sure they'd be big enough to do the job well.