Welcome to TFP!!
Put the leaf blower right up to the pipe and duct tape the 'bejesus' out of it and turn that puppy on
Do you have a valve on the MD pipe that you can close once it starts bubbling?
] You may be fine with the vac you've been using
tie a string to your pool brush and lay it across the MD. If you see it moving when you blow air into the line, water IS being evacuated from the line. Then you've got to 'guestimate' whether enough water was forced out to make the water level in the pipe below the frost line in your area.
I'm sure someone else here has a better way but thought I'd proffer my $.02
Please keep us posted as to your progress.