I bought a blow out attachment that you can hook to compressed air. I was surprised by how much water came out of the hose and pump. I left it on for about three minutes and it was still a good mist coming out.
My question is as far as storing in cold temps is concerned is this sufficient or should I still put rv antifreeze in it too?
Why knock yourself out? For over about 3 decades, give or take I've pulled the cord, water squirted out of the pump, when the stream stopped I add RV anti-freeze then pull the cord until that comes out and cap it off. I never had a pump freeze doing that. The whole process takes a couple of minutes.
I want a volume of fluid in there that has anti-corrosive properties rather than try and blow it out. That method will most likely cause some form of corrosion, and excess moisture could freeze around small seals and "o" rings.
So in answer to your question, yes put the RV anti-freeze in there. HTH