Here's the detail on how the scraper is able to remove the stubborn aerial roots even in tight corners.
For this job, I devised this long handled scraper by binding a spatula to a long rod using duct tape.

The danger with this job is the falling debris as the dried aerial roots get scraped off. So exercise proper precaution. As shown below, wear safety goggles to keep debris from falling into the eyes and wear a hat since the debris can get into the hair.
Use a ladder to reach the topmost areas. Be careful when working at the top rungs of the ladder and ensure the ladder is safely secured to the ground and wall.

For the truly hard to remove roots, use a toothed paint scraper as shown below.
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