So a new or reconditioned reel to reel machine with variable pitch would be a worthy investment for serious transcriptionists. Also, mini-cassette machines routinely have two speeds although the fidelity is not as good as either cassette or reel to reel. In approaching the transcription of solos, the first step would be to begin to identify typical melodic intervals used by the soloist. This becomes easier once you have mastered the ear training exercise as described above. The next step is to develop a rhythmic understanding, and rhythmic notation, of the soloist.
Some soloists are so precise in their rhythm that it is a breeze to get it on paper.
It is important that the beginning transcriptionist attempt simpler solos at first. If you attempt something so complex that you become frustrated it may turn you off. This will not happen until you have done this a lot. In fact, many times it is possible to visualize the entire phrase. This is the quickest way to get something as opposed to picking it out note by note.