Much depends on the subfield, but here are two shortcuts to understanding a dense paper:
1. Many CS papers are presented at conferences, and many of these talks are recorded and available.
2. Look for a paper citing the one you are interested in. The “related works” section often contains brief summaries, which are written with the benefit of hindsight.
Somewhat related, an earlier comment of mine on how to acquire copies of a paper without resorting to unauthorised copying [1]