E-commerce exports - how to file under exports with 0% gst?

We are a small e-commerce exporter of mobile accessories with our item values ranging from 300 to 600 Rs per shipment with a overall volume of Rs. 6 to 7 lakhs per month. All our payments are received through Paypal and items are shipped through Post (fulfilled by DHL E-commerce) to countries all over the world. There are tracking numbers available for 50% of the shipments whereas other 50% are shipped without tracking numbers through regular Airmail. Currently we are paying 18% IGST for all these small exports. We have taken LUT for exports without payment of IGST. How can we file these exports under 0% GST and what documents can be submitted to the Dept as proof of exports?