As for gear, it can still get a little chilly at night even in May in
the Mountains, so I'd make sure you at least bring a fleece sweater to
wear, and at the very least least a 40 degree sleeping bag. I'd go with
a bag that was rated for 32 degrees myself, but I rather be warm at
night than cold. The shelters anywhere along the AT in VA can be full
up pretty fast in May, so you should bring a tent too.
You'll need the four days of food. You don't want to waste anytime of
your four days in the woods having to hitch to town to get more food.
Water you should be able to find every day especially at shelter areas,
unless there is a severe drought between now and May, but you should
treat the water. For four days I'd go with iodine, instead of carrying
a water filter, but then I'd be carrying the weight of KoolAid to cover
up the iodine taste, so it is probably the same in the long run.
And Virginia is relatively easy when you are in good shape, but after a
winter stuck indoors, you may find it a bit tougher than any rating you
might have read, but if I had to reccommend a 4 day hike to someone,
not based on ease, but on the sights and beauty in VA, it would be to
do a 50 mile loop hike starting out of Damascus, VA, very near the
NC/TN border with VA and hike north through the Grayson Highlands, one
of the most beautiful areas of the whole AT with semi-wild ponies
roaming free, then when the AT meets up with the Iron Mtn. Trail hike
south on it back to Damascus. It would be a pretty damned tough 4 day
hike though.
Have a Great Hike!
Kurt