Since you're close to where I have to get on normally to go to Monash I might go a bit further than what you've asked here

(also I'm procrastinating something atm), although most of the information is in the link above.
From Huntingdale station, cross the road that the underpass exits at (during the morning when uni is on a lot of people jaywalk, and I swear someone will get hit one day). Then the bus thats normalyl the quickest is the 601, although that is due to the the frequency of the bus normally, which is less on non-uni days (not sure about weekends), but on uni days basically by the time you walk to the bus stop you have to wait a couple of minutes max (most of the time when its not busy one leave as the next arrives). There is also the 630 that comes that can get you there too (and possible the 900 in the right direction, but its slower iirc).
As to which line is quicker, well it depends on what time you're there, and what trains are waiting for you when you change across the one platform at flinders. During weekends everything is going to be different, but during uni times in the morning most of the time you'll get express services (which is good, cuts a little bit of time off the 90 mins or so).
On weekends however, you will probably take a bit longer than usual as the trains aren't as often.
My record is 72 minutes from a station or two past you, and worst is like 2.5 hrs (without a line cut that is).
EDIT: On looking at it, the 601 doesn't look like it runs at this time of year, so if its not there then the 630, 630a are the ones to get on (I think...)
Anyway hope that helps
