I did a full Currie grid test program a few semesters back. I cut overall volume of glaze to about 1/3 of his recommendations, and only mixed 'batches' for the four corners. The glaze mixtures for the remaining 31 spots were created using syringes to produce just enough glaze for each spot. It was easy to figure out how much glaze was needed to cover each spot on the grid tile and to work from that to how much is needed from each corner batch. The limitation ultimately depended on the smallest amount that can be measured accuratly with the syringes on hand. Everything then scales from that amount. All the calcs were done in a simple spreadsheet so I only needed to squirt so&so ml of slurry from each corner bucket into a pill bottle, shake(not stirred), pour onto the proper place, rinse the pill bottle, and repeat. In the end I still had significant leftovers in the four corners, but much less than if I had exactly followed Currie's program.
My conclusion for his 'program' for the overall exercise was to make it overly simple to potters that are intimidated by arithmetic.
Overall, the approach of using volume blending along with the multi axial line blends is both sound and efficient. The large batch sizes are to reduce the effect of small random measurement errors. It can improve precision, not necessarily enhance accuracy.
Having some 'grit' in porcelain does create interesting surface textures -- both visually and tactilely. Try using some local sandy clay, especially yellow and orange clay.
I like using clay from our ponds as an exterior slip to cups and bowls and glazing only the interior surface or wedging it into white clay - like porcelain - to add some excitement to an otherwise boring surfaces.
Lots of ways to modify a bag of clay to make it your own.
What I find interesting from this discussion so far is that the non-pottery consequences of unavailability of electric power for the coming 365 days has not been considered.
I can't make pots when there is no ice cream available at snack time. And, while I do enjoy walking 2 miles to the store for an ice cream bar, I don't really want to tote that bag of clay back to the studio because there is no power at the gas station to pump gas into the truck that I normally use to go get the clay and ice cream. But wait a minute, I can't buy ice cream at the store when there is no power to keep it frozen or run the cash register to make change for by fiver.
Thus, I will sun bake my pots, just like I did when I was 4 years old.
One way to better control of the fan is to add a tee in the air line between the blower (fan) and the burner to split the air into two streams. Install a butterfly valve on the side of tee and use it to divert air away from the burner. Run the blower without throttling the air intake to the blower. The blower will stay cool, and you will have control over air to the burner.
Re the 'yellows' along with the 'eggy' smells could be due to odorizer added to the propane to alert you of leaks. Some regions mandate that gaseous fuels have the odorizer to alert everyone for leaking gas. In the US it is required in natural gas, not sure about bottled propane. The favorite odorizers here are sulfur based. Check your fuel supplier.
Robin Hopper's books "The Ceramic Spectrum" and "Making Marks" (available from CAD bookstore) are good starting points also but his approach is less chemically oriented and more experimental -- empirical. Robin understood the chemistry but was interested in the outcome, not the process.
Potters seem to have concocted a pseudo-chemical glaze vocabulary that makes sense only to potters, so when reading a real chemistry textbook you need to be aware of the differences in the meaning of ordinary familiar words such as "flux," "melting," "bonding," ... ; modern silicate melt science does not use the Seger "unity formula".
Remember this ain't rocket science, it's just playing with mud and hot rocks.
Spray soda ash (or bakiing soda) on unglazed bisque ware before loading the ware into the kiln. You can get "flashing " on most clay bodies with this technique. Slips can help too. You don't have to have a salt or soda or wood kiln to get the effects.
Test test test
vary how much where you spray and where you don't spray