First make sure that it is properly identified as crabgrass. If it's confined to a relatively small area, pulling it out by the roots is the best option. Roundup will kill it, however it kills everything that it gets on. For larger areas look into a systemic herbicide for the best results. Soil temperature is a factor with systemics also. Read and follow all labels prior to application.
Bug busters has been around for a long time. They probably have more knowledge than a random Lowe's employee
Have you tried asking at maybe some place like Lowe's, they carry a whole array of products that will work on your lawn.
It's best to call Bug Busters, they have better knowledge than I do.
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