At first , it seems like a good idea, especially considering the wide variety of grits available. But it is not without caveats.
Sandblasting is great for initial scale and rust removal.
It is also a very effective method for "prep" operations; if a surface is to receive a coating of any type, then you can effectively double the surface area by sandblasting, which will significantly improve the bond between metal and coating. (This is also why a sandblasted surface is more prone to oxidation.)
Beyond residual removal and surface prepping for subsequent operations, the effective utility of the sandblasting method is really going to depend on the design of blade you wish to make, and the standards to which you adhere.
For example, any design requiring crisp, well-defined lines will not be a candidate for this method.
It can provide a decent satin finish, providing the condition of the surface is already where you want it. This is important, because there is a difference between the way the abrasive is applied to the surface, and the resulting effect of that particular application.
For example, it will not remove scratches in the same manner as a sheet abrasive.
This is a control issue, because what we are actually doing during scratch removal is taking the metal outside of the scratch and bringing it down to the same level as the lowest point in the scratch. Easily accomplished with sheet abrasive and a backer; not so with loose abrasive.
When using loose abrasive in a propelled manner, it is allowed to penetrate into the scratch. The end result is that while any scratches will appear to "blend in" with the rest of the surface, the depression itself is still there. The higher in grit progression you go, the more noticeable this becomes- instead of appearing flat, the surface can now appear to have a slight "wave" defect when observed under scrutiny.
Another concern, at least in my experience, is the grading of the bulk blasting abrasive in comparison to that used for quality sheet abrasives. For example, if you specify 400 grit, no abrasive grains should be larger (coarser) than 400 grit. But a portion of it is allowed to be finer.
Grading is determined by the manufacturers, but as a general rule, more consistent grading (meaning the abrasive is within a set parameter to the size specified) equates to higher quality and thus higher cost.
Inconsistent grading can also apply to sheet abrasives, but usually only those of the very lowest quality will suffer this effect.
Please keep in mind that I speak in terms of what is typically available to me from a domestic standpoint; the abrasives you acquire most likely fall within FEPA guidelines, so the above may not even be a consideration for you.
There are some here who do use sandblasting procedures as part of their regimen, and do so successfully.
My recommendation is to consider it a useful part of your tool arsenal to be used in conjunction with the other methods, not as something to replace the other methods.
The primary purpose of the different grits of blasting abrasive is to provide different textures on different materials; any visual effects are to be considered a byproduct of the process.