I saw some techniques discussed about tinting RC car windows with markers. I'd like to share an effective solution I found: stick-on tinted film advertised for headlight/taillight wrapping. It's got an adhesive under a removable backing and remains removable itself. Keeping the sheet that the painting masks come on makes it easy to cut out the exact shapes you need for the shell. The final effect is subtle but present:
Less than $10 for several feet of it here. One tiny detail, it's got disposable liners on both sides. I fooled myself into thinking it wasn't self-adhesive at first after removing a liner and not finding the adhesive, then later realized it had another liner on the other side.
Less than $10 for several feet of it here. One tiny detail, it's got disposable liners on both sides. I fooled myself into thinking it wasn't self-adhesive at first after removing a liner and not finding the adhesive, then later realized it had another liner on the other side.