Ive tried sodium carbonate in a dry tek experiment and it seems to work using ethanol to do the first pulls, even though sodium carbonate doesnt raise the pH too much... If you do an a/b and want to try using sodium carbonate, use a lot of it (saturate the solution), and use a stronger solvent like limonene or xylene or dcm etc. With shellite the yield will probably be poor.
Two other things about sodium carb is, when you add to the acidic solution, it will start foaming, so add it very slowly.. Also, there will probably be more emulsion, so dont shake the layers, stir, and if emulsion happens add a lot of salt.
In any case, if you have patience, do with part of your material a different tek using sodium carb or whatever, and compare the results, and let us know how it goes
As kash said, if it goes wrong you can always add lye and pull again