Interior paint used on exterior...Now what?

This is the picture that goes with my forum question.  Couldn't figure out how to upload it from my computer, so I pretended it was a video.

Since this is an exterior wall I would try a pressure washer. To start out hold the wand back far enough not to take any paint off, then slowly move it closer until you get the results you want.  Just keep the wand moving back and forth so you don't make any cut marks.

You could try softening the paint first with a paint stripper there are Eco-friendly safe alternatives available that are water based and effectively lift paint from surfaces without harmful risks unlike their chemical solvent counterparts. Rinse with a pressure washer for instant results.   

Use a citrus based stripper that will cling to the wall and allow it to work overnight. However, an easier option would be to paint directly over the exterior paint with a good quality interior latex paint.

Rub this wall down and paint with exterior paint.

Exterior painting in London

Make it clean by removing paint and apply laminated external paint,