In most cases, I'm not a proponent of major defoliation but I do rip a few leaves off every now and then.
I take the bottom leaves off so that no leaves are touching the soil but I don't lollipop very high. I stop where the branching begins or just above this area with the purpose of increasing air flow. Most defol that I do is to increase air flow to minimize the risk of PM and bud rot and such. Some strains do better if some of the leaves are removed, some don't need it (longer node distances), and some won't like it very much. I guess it's a case by case thing for me but I don't condone just ripping leaves off without any forethought and a game plan.
For increased light penetration I usually just tuck leaves back.
IMHO any major defoliation should be done before flip to minimize stress. Light defol can be done into the second, maybe third week of flower but doing it any later may be a stress trigger for a plant to go hermi on you.
Back in the day I used to defol big time. The reason I did so was because it used to get "dry" during the grow season and flag leaves were worth their weight in gold.
At times there was no weed to be found because of the War on Drugs push so we smoked a lot of flag leaves during the dry spells back in the day. Now that I don't need to smoke the flag leaves I tend to leave most of them on now.
I think Growlow and CajunCelt have you covered with questioned that you had regarding hash making. I think both of these guys have much more experience than I do with this so I'm really glad that they were so kind to offer their advise.
Thanks fella's!!