The park didn't close to MNSSHP guests at all - ie we went back in after a break at around 6.15pm, the park closed at 6pm officially on Friday, but obviously there were still a lot of non-party guests still on Main St at that time. By 7pm security and CMs were checking everyone for wristbands and making sure that those without were leaving the park. If you had a wristband you could go through to Fantasyland, Adventureland and Frontierland, where the MNSSHP rides were open to ride (ie they never closed those rides between park closing time and MNSSHP start time at 8pm).
Just after 8pm the characters appeared in Fantasyland (look near the rides - POTC, teacups, Pinocchio, Peter Pan, Dumbo, and between Auberge de Cendrillon and the carousel - oh also IASW), I guess it would have been the same in Frontierland, just as you come through Fort Comstock, and over by Phantom Manor.
The shows started at 8.30 I think, and went on every half hour or so until 10.30pm. The characters were out most of that time too. Then it was the cars n stars Halloween parade at 11.15pm, followed by meet n greets down near the bandstand (we left at around 11.45 after meeting Esmerelda and Clopin, and there were still loads of folk in the parks gathering autographs and photos).