If you use a blower (such as from a wet/dry vacuum, or from a leaf blower), you'll be able to blow the pipes to the skimmer(s) and the return pipes to the pool. You will most likely be unable to blow the pipes going to the intake at the bottom of the pool (if you have one). The 3HP-6.5HP air pump will be insufficient for that water column. You'd be asking too much if you try this with an air pump that is weaker than 3HP.
With a dedicated pool blower, you'll be able to blow all lines.
However, you do not actually need to blow the bottom of the pool. That area never freezes (assuming you're not that close to the North/South pole). If you hire a pool company, they will blow the bottom of the pool as well. It will be quite evident from the turbulence that the air is coming out from the bottom of the pool. Once they're done pushing, the water goes back right through.
The key is to lower the level of the water far enough below the skimmer (you don't want rain/snow water to go back into the skimmer before the frost is gone). Another key point is that you must seal the pipes coming back to the pool. Estimating how far you have to lower the level of the water (you'll have to purchase these tens of thousands of gallons later from your water company) is perhaps the main art in doing this task yourself.