As pointed out by André Lwoff et al. (5) in 1962, electron microscopy is probably the most efficient approach to viral classification
Not a doctor, and I didn't read the whole article, but the above sentence struck me- are we supposed to believe a technology that more than 4 decades old is still the most efficient viral classification method? In the age of cheap and rapid DNA sequencing? Seem hard to believe.
A good bit of information on viral isolation (and specifically related to HIV isolation) can be found at this link on
HIV Isolation. Several articles there cover how to properly isolate a virus.