Help working with a scratched lens

I have scratched the mess out of my 24-70, and have an upcoming show.

I'm sure the repair place will charge me $600, and not have it back on time. I'm wondering if anybody knows about any quick fixes?

I've heard of sharpie over the lens scratch, but I'm not sure which. Pen, or felt tip?

I've only noticed a slight flare when shooting something bright like lights.

Any tips would be very helpful thank you.

(Car keys) .... I will get insurance next time.