DPF issues...

[Nine468]

Over the few years ive had my car, ive had a few dpf issues.
Its been into the garage for rectification, each time they fixed it. They sprayed some dpf cleaner into the dpf..[ NOT just the stuff that goes in the tank], Then force regend it...
What im asking about is where will they have sprayed the cleaner in. Is there any accessable sensors that are removable.
Im guessing there is..
I would ask my garage, but im not sure if they be forthcoming with the info....Protecting there investment etc....
Im pretty handy with cars etc, so im contemplating getting a Carly app thing and doing forced regens myself, as and when its needed.
It cant be rocket science,, can it...

[X5Sport]

At a pure guess probably into the oxygen or back pressure sensor port upstream of the DPF.  Wind it out, squirt in fluid, wind it back in.  It's what I would go looking to do unless there were clear instructions as to where else in the exhaust system is goes.