The rhetorical argument that laboratory courses are crucial for training skilled STEM practitioners is ill-evidenced in teaching practice. The arduous task of implementing instructor-led skill assessment in large-cohort courses and persistent student "disengagement" from its educative goals are some obstacles. This study emphasized the need to equip learners to self-assess technical skills, supported by explicit performance standards and objective evidence. It trials two interventions, a self-assessment (SA) checklist and a learner-recorded video, to examine how the combination impacts the appraisal ability and attitudes towards SA. The participants were from a first year chemistry course in a biotechnology and chemical engineering course. All the participants self-assessed titration competencies against a checklist, with about half assisted with a video replay. A video critique task showed a significant main effect by intervention. SA-with-video participants scored higher than SA-only participants and the control group. The additional video intervention did not produce any significant gains above SA alone. Qualitative analysis revealed that SA-with-video participants were more targeted in their critique responses. Video differences in attitudinal responses towards SA were not prominent. Selected SA items related to perceptions of the value of SA in skill improvement, and, as a future study strategy, goals and commitment of using SA for skill improvement, were associated with video exposure in the biotechnology course, or with the course in the video group. Improvements for future work are discussed.