Taking fleeting notes about the material while you're in the process of reading it highlighting works too in a pinch, but it's worse, as the level of engagement is lower
Another level of processing, in a way, is apply Spaced Repetition to evergreen notes that you want to remember or periodically rise to attention. I've been applying this to first level of processing mostly so far. But this is something that can be developed further, I feel like I haven't discovered it's full potential yet.