Can I layer Lustre & Jet? If so, which is the base layer?
The quick answer: Yes, of course you can layer Lustre & Jet for maximum effect; Lustre is the base layer, and Jet is best applied on top of Lustre. There is no need to apply multiple layers of either product. Full performance
The detailed answer: Lustre contains particular resins & filling agents that are capable of masking light/mild defects in your clear coat, if present. Because of this, Lustre is best applied to directly to the clear coat, maximizing its benefits.
Jet is designed to create an aggressive hydrophobic effect and will add sharp shine and reflections to clear coat, ceramic coatings, and even Lustre itself; thus it will be used as the second and final layer so that its hydrophobic properties are maximized.
The combination of Lustre and Jet will rival most mass-market ceramic coatings in terms of gloss, UV inhibition, and water behavior. They are certainly worth layering as they were designed with two slightly different goals in mind, and each set of properties complements the other.
Should I wait a certain period of time before applying Jet?
No. You can apply Jet immediately following the application of Lustre.