Are you making an extract batch? If so, why not take 1 cup of DME or 1 1/3 cup of LME, and add it to four cups of boiling water. Cool it, pour into a sanitized growler, add the yeast, cover with sanitized foil, and you have a starter. Let it ferment out, and then pour the whole thing into your wort when it's cool.
Right from Wyeast's website:
Usage
The Propagator package contains a minimum of 25 billion cells in a yeast slurry. This volume is not adequate for direct pitching into 5 gallons of wort and requires a 1-2 L propagation step prior to brewing. The Propagator is designed, when propagated in a 1-2 liter starter culture, to inoculate 5 gallons of standard strength ale wort (1.034-1.060 SG) with professional pitching rates.
So, you don't even have enough yeast for a 1.034 wort. If your beer is bigger than that, you're even more seriously underpitching.