Multisampling is far too much of a headache for me to accomplish with any level of quality on my own.
The secret here, for me at least, was SampleRobot.
LadyGaia suggested it in a thread on GS. I was initially sceptical, but since I have a Yamaha Montage and Yamaha were offering the Montage-specific version for free I decided to give it a go. It turned out to be an excellent product that can fully automate the process of sampling a MIDI controllable synthesizer and, with some practice, can also automate the otherwise extremely time-consuming process of looping the resulting samples. So I upgraded the Montage-specific version to the full product with a view to using it to create samples for an unrelated project I'm working on.
The process of creating the OB-6 and Erebus sample sets was basically one of setting up a series of SampleRobot projects to record the relevant note ranges for each waveform, making sure the levels were appropriate, and then leaving SampleRobot to get on with the job. LadyGaia subsequently handled the looping of the samples, and did an excellent job. There's something of an art to setting the parameters that control this process, and at the time I was still very much at the learning stage.
I'm happy to hear that you - and others - are enjoying the results.
But if you are interested in doing something of this kind yourself then SampleRobot really can take the majority of the pain out of multisampling, particularly when sampling a synthesizer.