With your capstone assignment in place, you’ll be able to build "backwards" through the term, ensuring that each one of the preceding assignments gives students the right opportunities to acquire and/or practice the skills and competencies they will need in order to tackle the course's grand finale. To be sure, this kind of scaffolding give students the intellectual skills they need to take on the highly synthetic, creative tasks associated with capstone assignments. More than just that, though, it also allows them to develop these skills step-by-step and gives them time to reflect on their development—which in turn gives them more awareness of, and confidence in, applying these skills to "bigger" challenges.
Scaffolding is important for both "traditional" and "creative" assignments. In the case of traditional assignments (like academic papers), students benefit primarily from the sequential accumulation of analytical skills. In an Expos course, for instance, a Unit 1 assignment often asks students to make an analytical argument about a single source, a request which might not be 100% clear to students when they first encounter the prompt. Over the following few weeks, though, students will move from learning strategies for active reading to ways to develop analytical questions about a source to how analytical questions are answered by a thesis to how a thesis is an arguable claim supported by evidence to how a thesis supported by evidence and analysis is an analytical argument. In that way, each skill learned in the unit requires the previously learned skills and paves the way for the next, higher-order skill that will culminate in the essay assignment students were introduced from the start.
In the case of creative projects, it may be necessary to provide scaffolding not only in analytical skills, but also in the basic tools and genre conventions of the medium within which they are working. Just as students often complete lower-stakes writing assignments in advance of an essay or research paper, students who have been assigned a creative project need to practice working with multimedia—not just on the production side, but in terms of making arguments, citing sources, and developing a voice, well before they attempt a final project. Small-scale multimedia work can, for example, be evaluated on a complete/incomplete basis, since it's meant to serve as practice. Then, when it comes time to attempt the end-of-semester video, or website launch, or virtual exhibit, you'll find that the overall level of student work is high enough that you'll be able to grade this non-traditional work using many, if not most, of the very same criteria you'd use to evaluate traditional papers.