Transplanting into DWC..Need some help.

Need some helps on techniques with transplanting plants into a Deep Water Culture system. I use vermiculite to germinate, and allow the plants to grow up to about their second leafset, growing up it's third. The roots are slightly developed, although Im not sure if I should allow them to grow larger in the vermiculite to get a better result with transplanting. Anybody got a few suggestions on transplanting from vermiculite to silica stone?