The early pioneers in genetics were all consummate hackers in the truest sense. For much of the work they were doing, the had very little information about the underlying processes to go on. The were, in effect, reverse engineering life.

It's also worth noting that Sanger's sequencing method, or variations on it, were still used decades later to produce the bulk of the human genome sequence. Only very recently have newer, faster, alternative methods been developed. Even so, Sanger sequencing is still used for smaller scale studies, and is simple enough that almost any modern biology lab can do it on their own (all you need is a thermocycler, some eppindorfs, a sequencing gel apparatus, some photographic film, and all the raw chemicals).