in regards to the airway over the field....

I did that once with an airway about 18 nm away and when filing they asked me my route to that airway.

I didnt know what to say.

I could have told them direct to a radial/distance on that airway, but how would you actually navigate?

Just draw a line and fly a course corrected for forecast winds? (if departure doesnt have VOR on the field or you cant use a nearby VOR radial that you can extend through the airport and fly it to a published route)