I would imagine for that quantity you'd need to drill into the tree slightly and make a small drip tap for the resin to trickle out of. But im only guessing.
For small quantities you can pop the small resin filled blisters on the trunks, but would take a long time to get a cup full. I did this when playing around trying to make some pitch and was able to harvest enough in just a few pops.
Either way you'll probably end up making a mess all over your skin and hair, just like i did when one of the blisters poped the wrong way...so heres a little tip for you. Pine resin is oil-soluable not water-soluable so comes out really easy if you use olive oil on a tissue and use it like a wet wipe.
Have fun.
**EDIT** Just read Bam's reply and that seems far more sensible that drilling into the tree causing unneccesary damage.