Forget about the bioguard products. You don't need them, and they certainly have nothing to do with blowing the lines out.
Are you certain the lines were never blown out before? Part of it depends where you live and how cold it gets.
While every pool is different, the basic idea of blowing out the lines is to remove water from them that may freeze and therefore expand causing damage. I personally use a Rigid vac from Home Depot to blow them out. I disconnect the pipe from the outlet of my filter then blow through it until only air and no water comes out of my return jets. Then I cap the jets off.
For the skimmer I use the vac to suck the water out of the hole that heads to the pump, then blow back through the hole from the pump to the skimmer to be sure all water is removed. It is then capped with a "gizmo"
As you can probably tell there are many different ways of accomplishing the same thing, and each pool is very different.
Hope this gets you thinking along the right lines, anyway.
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