I almost always use crushed grains that are 6+ months old. I like to buy my recipe kits when the price is too good to pass up ($20 or less is my sweet spot). So when there's a big sale, I'll stock up on a dozen different kits and brew them throughout the year. I've brewed with crushed grains...
How about if I do a "poor man's sparge" by pouring a quart or two of heated water over the grain bag? Or, maybe I should start by transferring the grains from the muslin bag to the grain bag I already have (and already use for additional grains that I like to augment my recipes with) before I...
I don't want to derail the conversation, but I have a question. For reasons of space and simplicity I'm an extract brewer (I buy my kits online from various HB sites, usually whichever one is having the best sale at that moment). Every single instruction sheet I've seen always explicitly...
Have you tried gypsum? I always toss a teaspoon or two into my brew kettle when I want to accentuate the hop character of my beers. Probably wouldn't hurt based on the description of the problem you're having.
The worst part is, all that suffering over a stinking Mexican Lager! We don't need no stinking Mexican lagers! ;)
Hope you heal up quick and can get back to brewing some (ahem) ales. :D