We did a rush retreat every year - not a real "retreat", but a weekend where we spent both days, 10-6 or so, in a function room on campus, just preparing for rush.
For conversation skills, we paired off, with one person acting as the sister and the other as the PNM. The PNM often had some character flaw (shy, slutty, etc) that she had to act out.
A word of advice on songs: Don't practice the same one 50 times in a row. Our rush chair made us do that with one particular song, and I was sooo sick of it that it was all I could do not to run screaming from the room when we had to sing it during parties! Mix it up... if people aren't learning a particular song, revisit it later in the workshop.
We didn't do a fashion show, but everyone was told what to have on hand. We did dress checks during work week - we just showed the rush chair what we planned to wear, and were reminded to try everything on again to be sure it still fit.
Hope this helps
