Repitching yeast?

So I have a little bit of a dilemma. I brewed an IPA yesterday and pitched harvested yeast slurry that I harvested at the end of September. Mr. Malty said it was 12% viable and that i should pitch 600ml. So I pitched a little more than that. But I need this beer to start fermenting quickly and finish quickly. I'm trying to get this beer ready to take out of state for my family on Christmas (I know I procrastinate). I know the age old advice to RDWHAHB. But I am curious if anyone thinks that i should pitch some more yeast. I have a 1056 slap pack in the fridge that I could use. My goal is to rack to secondary next weekend, dry hop for a week and then bottle condition for a week and half and hope its ready. :-\ But for it to be done fermenting this weekend (or close enough to it) I need it to start soon. Thanks in advance. And I normally don't try to rush the brewing process, i'm just under some time restraints. Thanks!

You can always pitch more yeast, but I am not sure about how much of an improvement it would make in your fermentation time. Also, there are a few considerations. First, if you were to pitch a 1056 slap pack, and this yeast differed from the yeast slurry that your had previously harvested and pitched, you will have two yeast varieties contributing flavors to your beer. This can be a very good thing, and many people love to pitch multiple yeasts to get their desired flavor profile, but it is important to consider. Next, it is important to keep your fermenter around 70*F (of course this depends on the beer style and the yeast, but 1056 loves 70*F) and your wort oxygenated to really achieve a fast and good fermentation. Last, its good to consider the OG of your wort. If it is much higher than 1.06, then I would really recommend pitching additional yeast if you want a quicker fermentation. If it is lower than 1.06, then you may be fine not pitching any extra yeast and just keeping your fermenter warm and your wort well oxygenated.

Check your gravity.
I wouldn't do anything without measurement, if it doesn't drop after ~72 hours I would consider repitching, but wait at least until then.
At what temperature you are fermenting?

+1 on the temperature. If you brewed on Saturday, the yeast should be humming along nicely now. Keep your room perhaps a little warmer than usual, at least for the next day or two to help kick start it.

It will take a little time to get going, being about two months old, and the temperature being low, but when it gets going I bet it will take off like gang busters very soon. IME Mr. Malty estimates viability low. For a batch I did recently Mr. Malty estimated 12% viability, the next weekend I brought what was left of the slurry over to my brother, who is a microbiologist, and he counted 90% viability and the cell density was also higher than Mr. Malty indicated.

More details here:
http://woodlandbrew.blogspot.com/2012/11/counting-cells.html

Thanks to all for the suggestions, I kept shaking the carboy and aerating, and did not repitch. I started late afternoon, and is now going off like Mt Helens. I wasn't expecting it to go this strong. OG came in at 1.068(the weakest beer I have brewed). Had to put the blow off tube on it after it decided to go ape **** all over my kitchen. But all is well here. Again thanks for help! BTW my house is set at 72, and my fermenter says that my brew is 69 degrees.

Oh, 69 degrees. I'm sorry, For some reason I thought you were fermenting below 60. That must have been another thread. Its good that it is going now, but you may want to drop the temp a little if you can. 69 is warm for most yeasts.

What type of yeast are you using?

Here is an example of a water bath and ice:
http://woodlandbrew.blogspot.com/2012/09/swamp-cooler.html

why not dry hop in the primary, as fermentation is finishing? that will save you a few days

Sure, if you are in hurry I would dry hop on day 10 and rack 5 days after.