A thin, thumbed wash mitt for reaching in and around the frame (and other areas). Made from soft, absorbent microfibre with an elasticated cuff.
Once you've tried a microfibre mitt you'll throw out your old sponge... there's more control, more feel and less chance of dropping it (so less chance of it collecting dirt).
Maintenance is simple, and far more thorough than rinsing your sponge under the tap. After use, just machine wash at low temps (non-Bio liquid) without fabric softener/conditioner. Then tumble dry at low temps.