For the past year I've been thinking about how to eliminate those dots of light, experimenting with different products and methods. I've focused on layering blackout so that one hole is blocked by another layer of blackout. My secondary goal is to make this process as quick and efficient as possible.
Here's my favorite method so far.
These shades were made with an inner layer of Bella Notte Duette, to provide an interlining-like layer, with Silky Blackout on the outside.