I've been using a tool like this for years now. This tool makes cleaning your interior glass a lot easier since you don't have to stretch over the dash or rear seats to try and get into the corners of your glass. Using this will help you get completely spot free glass. This is a good tool to have in your detailing kit.
Straining and stretching to clean hard-to-reach glass can be irritating and even dangerous!
The Original Invisible Glass® Reach & Clean Tool. It combines an ergonomic, long reach handle and large triangular pivoting head with two washable, reversible, microfiber covers to make automotive glass cleaning faster and easier than ever. Ideal for all hard-to-reach areas! To make automotive windows shine, wash and rinse first, then clean and dry with the Reach & Clean Tool. No more twisting and contorting to clean angled glass, backhanded reaching into narrow spaces, or crawling over seats to get closer. Now you can reach it AND clean it with no streaks and no lint!