If your not pulling the pad, one has to ask themselves, just how deep do I want to try to dig.
Do you really want to attempt reaching under the pad to the subfloor?
Even if there is likely urine that has reached the subfloor due to heavy contamination?
Assuming you have explained to the customer that the "right" way to do it is by pulling the carpet and pad, and they are opting for lesser, CHEAPER service that may only offer an improvement, I think it is often better to not potentially open a can of worms by trying to remove any heavy urine deposits that have reached the subfloor.
If urine has likely reached the subfloor, especially over multiple areas, and the customer does not want to do it right, then I'm most likely not going after it unless it's only a small area or two.
If there is urine present at the sub floor, you better be sure to flush enough of it out if you have gotten it wet, activated it, and are now driving it into absorbent wood.
The poorest way to control the penetration depth of common padding treatments like OSR is by "pouring" it out of a container, nonetheless a 5 gallon bucket, so if your trying to avoid reaching the subfloor, then "pouring" any treatment is out of the question.
What I do want to reach, is down through the carpet backing and just to the top surface of the pad.
Anything deeper than that is another realm that does not like to give up it's dead, and has a serious lack of airflow for efficient drying.
I prefer applying my cocktail of choice with my HydroForce using enough to saturate the area enough that I think it will migrate down to reach just under the backing over the following five-ten minutes, and then extract and repeat the process a few times.
Finish off with some extra dry extraction and make sure the customer understands the importance of aggressive ventilation for several days.
I think even if going deep with the Homer bucket technique, multiple, short duration dwell/extraction cycles are better than one long duration over-saturation that allows the liquid to migrate around and soak deep into the wood and padding material.
It should be flushed several times anyway.
