We have the brother QL-500 label printer.

We simply copy/paste the PayPal shipping address into the label template we set up for the label rolls we have bought and print straight from the P-Touch software. Sometimes you have to fiddle with the address layout slightly to make it fit the label properly.

Very simple for us. No need to use any other labelling software or methods at all. At the moment we are sending around 10-15 envelopes per day. In better days this would normally be 25-30 per day.

Most of our things go out by large letter tho. If we get an order big enuff for a parcel we use click n send  500gm ebay satchels. Sometimes the 500gm express post satchels if the buyer chooses that option.