“what do I do in Jhana Four to further my insight practice?”
Until you take a retreat use the breathe as your insight topic. It is a wonderful object for meditation because of its simplicity and tranquility. You will be able to progress through all of the insight stages using it. Start by getting into the 4th jhana and then directing your attention to the breath.
“Is it true that people are getting good results from Goenka methods?”
Very much so. All of my paths and a friend's paths have come from it. It’s just that people are a little more discrete about their attainments due to the nature of the organization. With regard to the efficacy of the technique understand that the whole Anagami path is entirely about the body (the body turns out to be synonymous with sense pleasure) so the fact that he has you working with body sensations from the start cannot be far off.
As I understand Nick did get stream entry on a Goenka retreat, but he did it by ignoring the instructions and doing his own thing.
Nikolai does not suggest straying from the technique here is a quote of his from his article on how to get stream-entry on a course
“If you are a beginner, keep developing your vipassana skills and follow all of Goenkaji's instructions to the Tee! Actually, that goes for everyone!”
http://thehamiltonproject.blogspot.com/2010/11/going-for-stream-entry-on-goenka-10-day.html
So anyway, do the breath (anapana) technique and report back how it goes!
-d