@akron3 Sometimes there just isn't a shortcut!
Here is the testing sequence and why it takes so long. Let's begin with the caveat that most strains of mycobacteria a very slow-growing, many that may be present in our cultures do not require treatment, and those strains that require antibiotic therapy are "picky" - only a few drugs are capable of killing them.

Sputum sample is produced, then stained in the lab to see if there are suspected mycobacteria present. If the result is "positive" the sample is then stabilized and sent to a specialized lab for further testing. Some labs send their samples to a central location for processing, some are sent to specific commercial labs, and some are sent to the lab at National Jewish Health (NJH) in Denver. As far as I know, all are reliable, but only NJH and a few other locations have the capability of reporting the count (or density) of the bacteria, which, along with other symptoms, can help the doctor in determining the severity of infection.
The sample is place on several culture plates and incubated for at least 4 weeks to see if a mycobacteria grows. It is then examined every few days for up to 8 weeks to see what grows.
If something grows, a technician examines the sample under a microscope, or sometimes with genetic tests, to see exactly what it is.
Once that is determined, specific antibiotics are applied to the slide(s) to see which ones kill the bacteria, or al least keep it from growing.
So, as you can see, the "bug" runs the show, and determines how long it takes to get results. When I was first diagnosed, the infection was so massive that it only took 4 weeks to determine I had MAC, and one more to determine which meds to use. The last time they grew my culture all the way, it took 8 weeks, and the only bacteria that grew were of a variety not treated.
All that said, research is underway to find a faster, but still affordable way to speed up the process. This is only beginning clinical trials, so we are probably looking at a few years...not months...before we see a change.