Dip the paint brush into the paint remover. The same company that made the model car paint likely makes a paint remover that would work well for removing the paint it manufactures.
Brush over the paint with the paint remover. Keep the paint remover over the glow-in-the-dark paint only or it may remove the original wall paint unintentionally.
Scrape the paint from the wall while the paint remover is still wet. Once the paint remover dries it is no longer breaking the bond of the paint and will not help in removing it.
Touch-up the wall paint if necessary.