The pears are covered with spines and tiny stickers (glochids), so don't handle these with bare hands. Tongs and/or gloves are needed. The glochids are in the white spots and around the base and blossom scar. Select pears that come off the plant easily with a slight twist of the tongs.
Collect in a dish or bucket. The next step is to burn off the glochids. This really isn't optional if you want juice or jelly. No one wants a mouth full of these spines. So, using the tongs, you burn them off. Easy sources of fire include gas stove or grill burners. A butane or propane torch or unscented candle, preferably beeswax, will also work. You should be left with black ash spots where the white spines were. After burning the glochids off, place the just roasted pear in a clean dish, NOT back in with the unprocessed ones or you'll get more glochids on the roasted pears.
From here' you are ready to extract the juice. Some people put the whole pears in the blender. I don't, but am not sure my method is any better. Next step, I slice length wise and load skin-side up in a fine sieve to 'mash.' Mash with a sturdy metal spoon, then scrape the pulp from the skin and mash some more. The sieve is over a Pyrex measuring cup. I try to minimize contact with metal to preserve the delicate flavor. Put the skins in a glass dish to weep.
Once most of the juice is out of the seeds and pulp, I move the pulp to a smaller sieve and Pyrex set-up and allow it to gravity drip. This will produce more juice as the ruptured seed membranes slowly give up their juice.