SSD-SLF trick, what's that? Never heard about it...
Find a (or several, but one is enough) Sub-Surface-Deposit of wanted Metal / Mineral on an asteroid with the lowest spin possible. Collect it, then disable your thrusters and launch your SLF. Go at least 27 km away from your Mothership, then disable the thrusters of the SLF. Switch to Mothership. The SSD is full again. Collect everything, disable thrusters, switch to the SLF still parked at 27+km, rinse and repeat. If the asteroid has no spin at all you can even leave the thrusters disabled as you don't need to aim at all
Advised equipments: multiple SSDM launchers (one each ca. 200 tons of cargo) and a SLF, mining gear ofc.