Most dry yeast today simply nneeds to be rehydrated to give them a boost. But cell count is still a key factor if there is a certain profile you are looking for. For lagers, I simply pitch 2 packets of dry yeast in lieu of 1 for ales.
Dry yeast are packaged ready to be hydrated and pitched, optimally. You should not make a starter with them. If you need more yeast, simply pitch another packet.