You just quite simply dump your nand each time you buy a new game, in order to be able to extract the tickets required for NSP packing. This can be done with hekate using the nand backup function.

Then you need to obtain the required console specific keys via biskeydump from your Switch, along with other keys via kezplez needed for hactool. It also requires eticket_rsa_kek.

For minimal ban risk, delete your WiFi connection profiles, put your Switch into airplane mode, backup your nand, run biskeydump, follow the instructions for running kezplez to get keys.txt, restore your nand.

At the end of this, you will then need hac disk mount to dump PRODINFO.bin, and mount the SYSTEM partition.

Credits go to @Khangaroo for his original posting of the Switch SD dumping guide, which was not exactly the most user friendly guide, and to whoever wrote CDNSP, which served as the basis for this tool, in terms of figuring out how the NSP format worked. Also to @tubebar for providing me a nintendo switch, and the motivation to work on the tools.