Dry hopping is good and gives the cider a nice kind of flavor and aroma but if you're going for an Angry Orcherd kind of taste, dry hopping is not going to do that.... But Just for the hell of it, use some cascade and see how you like it....
My method differs slightly from Linda's...
I use .1oz per gallon at the very end of aging (Sometimes a tad more... If I want a heavy hoppy flavor I might use .8 for 5 gallons)
Leave in only 7 days.
I ferment in primary for three weeks to a month, then I age for three months and at the very last week I will dry hop.
AMAZING!!!
P.s. Don't worry about sanitation with the hops, Just add it... you will be fine...
Don't boil the cider and Just throw it in your carboy or bucket loose and then when it's time to rack it out make a little cheesecloth filter over your racking cane, Works like a charm...