Hi Grant,
To clean insides just make sure you keep your applicator against the glass to catch the water as you blade off. Then just blade the last few inches and wipe off with a cloth. If your new to this I would suggest a towel on the floor just to be on the safe side!
As for pricing, I charge the same again for insides if not 50% more to compensate for clearing off window ledges etc.....
Best wishes,
Trev