Reusing software processes from a Software Process Line (SPL, i.e., a set of software processes that captures their commonalities and variabilities) and automating their execution is a way to reduce development costs. However, to our best knowledge no approach integrates both aspects. The difficulty is to automate the execution of a process whose variability is only partially resolved (i.e., a value is not set to each variable part of the process). Indeed, according to projects' constraints, it is possible to start the execution of a part of a process whose variability is resolved, while postponing the resolution of the variability of other parts of this process. In this paper, we propose a tool-supported approach that integrates both aspects. It consists of reusing processes from an SPL according to projects' requirements. The processes are bound to components that automate their execution. When the variability of a process to execute is not fully resolved, our approach consists of resolving this variability during the execution of this process. We illustrate this work on a family of processes for designing and implementing modeling languages. Our approach enables both the reuse of software processes and the automation of their execution, while enabling to resolve process variability during the execution.