Background: Mining online accounts of practitioner experience can provide new evidence for software engineering researchers. However, we need methods for assessing quality at vast scale. Objectives: We investigate the challenge of finding high-quality grey literature, defining high-quality in terms of a document's relevance to the consumer and its credibility. Method: Building on previous research, we use a version of the case survey methodology for automating the identification and assessment of high-quality grey literature. Results: We develop a model of credibility assessment within software engineering research and demonstrate our case survey methodology and credibility assessment model in practice. We use it to conduct a grey literatur...