Frank,
What has been your experience with Silicone Shield that leads you to say its garbage? I am more than curious, because based on conversations with three builders and three plasterers who are using it, the experience has been generally very good, and I am planning to use it on my plaster on Friday. RPM's silica fume (pozzolan) component is also reported well from a large plasterer here, and silica fume as you say can do perhaps the best job of converting the calcium hydroxide to a more stable, less water-soluble compound (some tests at some percentages around 15% by weight have shown complete conversion of the CaOH. Silicone Shield also contains some pozzolans, metakaolin and finely ground silica compounds, although less than RPM, and is less total volume.
How has it failed for you?