Idont know anyone polishing scratchs out of windows,the easy way is dont put them there in the 1st place.make sure every thing u use is up to speck and clean and it shouldnt happen,well it hasnt to me yet,but not saying it wont,if you have a scratch try ringing auto window repair buiss,they can repair window screens so why not glass?might be expensive but maybe cheaper option
good luck
itsthingy@msn.comps if it works let me know