Need help w/ blowing out lines IG pool

IG Sylvan concrete pool

Need to blow out returns and bottom drain. 1st what size air compresser do I need?

I see there is an area for a grease fitting, I think, in the jandy valve area, is this where I would put a fitting from the compesser to blow out the lines? When I open the jandy valve the hole is very, very tiny.

there is also one in the jandy valve where the skimmer and bottom drain pipes come in.

return lines are too low to lower the water level.

I hope someone can help