It is well known that the progress of R&D projects has more and more begun to rely on the availability of individual experts who are generally scarce and expensive. The matrix structure considers periodic staffing of project teams which has been found to be efficient for non-scarce human resources but is impractical for individual experts. Our objective is to develop and evaluate an alternative approach for resource planning and scheduling that might be useful for project portfolio management. The method we suggest is an extension of a recently developed optimization model for a job-shop with several machines and chance-constrained deliveries. Our method determines in advance the hiring and releasing points of individual experts that maximize economic gain subject to chance-constrained delivery commitments. For this purpose, we use a simulation based on a greedy priority dispatching rule as well as a cyclic coordinate descent search-algorithm. A benchmarking of the staffing of project teams and the integrative methods shows that integrated planning and scheduling is a very useful tool for the decision-making process in project portfolio management.