Originally Posted by RaptorNCBC
I use the smack packs all the time. I usually smack them a day or two before my brew day and get them in a diluted wort as a yeast starter
Yeah, I agree with this route. I know the smack packs and WLP vials say they're good for 5 gal up to ~1.06, but that's highly debatable. According to calculators like MrMalty
and YeastCalc, a pack or vial (~90 billion cells at best) is only enough yeast for 5 gallons of wort if the OG is under ~1.03.
It's always good practice to make a starter with liquid yeast, even in lower gravity brews. Yeast health is probably (IMO) the most important aspect of making great beer.