"Grains" seems useless, since we already have "Grain", and "Process" seems much too general to provide sane result-sets for tag searches. Instead, I think we should rely on more specific tags that refer to parts of the process, like "Boil", "Secondary" etc.
The same could also be said for the "Techniques" tag, but there might be merit in keeping it since, IMO, it has slightly more nuanced connotations than "Process".