The procedure outlined is quite dangerous if you actually understand what is going on during this procedure (if you don’t then you should not be doing so anyhow). When reviving batteries via this method there is little need for a voltage in excess of your original Dewalt DW9095 battery pack (and in truth, it is better to rejuvenate cells individually and not as a pack) — it is the amperage, not so much the voltage, that makes the process work. More voltage, especially when combined with more amperage, only makes the procedure all the more dangerous and increases internal heating considerably (which increases internal cell pressures). But more importantly, the maximum allowable amperage should be strictly controlled during this procedure, something car batteries and arc welders do not offer.
Yes, 99% (probably more on the order of 99.9%) of the time it will work and nobody will get hurt, however that remaining 1% of the time can result in a Nickel-Cadmium battery literally exploding in your face — and Cadmium is not something you would want exploding in your face even if we ignored the whole “exploding in your face” aspect of it. One will get away with it most of the time, but nobody really wishes to be the unlucky one in a gamble like this.
If one insists on using this method, then at the very least there should be a ~30A fast-acting circuit breaker (for C & D sized NiCds) — DC Rated — to guard against a severely shorted NiCd battery, which can result in your cables being unexpectedly arc-welded to the NiCd battery — which then makes immediate disconnection all but impossible and all but guarantees an explosion without a suitable circuit breaker to provide the automatic emergency disconnection. And please wear proper safety attire, leather gloves and a full face shield during the procedure.
As a general rule it is best to rejuvenate NiCd batteries one cell at a time with a power source provided by one or two fully charged cells of equal size and capacity. This is a much safer strategy and often more effective overall.