As mentioined, signings at the track are a farce..pretty much you need to line up for 3 hours at least, and then the drivers come out in 3's (normally a Top tier driver and then 2 others) for maybe 15-30minutes at a time. So you just get something signed by whoever happens to be at the desk when you get up there. I didnt bother with this last year at all. (Signings happened on race day)

In saying that, last year Schumi and Rosberg did a signing at the Petronas towers on the Thursday, so you may have some luck there again this year with Hamilton and Rosberg, check it out when you get into KL

Pit Walk. We did the pit walk on the Friday, it was around 5pm local time. All just line up at a gate near the main pit grandstand and go under the track through to the pit area, wasn't too bad (not too crowded) and didn't get rushed through it at all which was awesome. Plenty of time to grab pictures of the cars and garages etc. Also as mentioned above, it does appear that Friday is a free day, as we never had our tickets checked once...something ive learnt for next time, since we bought a 3 days pass and one of the days is free......

After Party's. Wish I knew...haha. Last year since we stayed in KL it took an hour to travel to and from the track, and after spending all day in the sun and the heat, last thing we wanted to do was party...haha we just went back to the hotel and drank beer in the pool each night :P