I would NEVER spray anything onto the breechface while the striker was still installed. I might apply a degreaser to a Q-Tip and then clean the breechface with the Q-Tip, carefully avoiding the firing pin hole, and then apply a very thin layer of synthetic grease. Thinking about this, I should probably find a plastic rod that I can jam into the firing pin hole to seal it while I clean it. I mostly use synthetic grease in my pistol, which is less likely to migrate into the striker channel. If it is difficult to access the firing pin and/or striker to remove it to clean it, I would say that is one reason to NOT chose that gun.
Getting a bit of lube into the firing pin/striker channel is probably not a big problem if you clean the striker channel often. I think people are mostly worried about the lube collecting gunpowder residue and clogging up. One of these days I am going to actually LUBE the striker channel with synthetic grease and see if will still fire an empty shell case with a live primer. I'm betting that it will still fire.
With a removable barrel you can hose it down with brake cleaner, bore cleaner, etc., and then lubricate it and wipe off the excess lube, no problem. It doesn't need to be degreased. You mainly want a very thin layer of lubricant left in the barrel to protect against corrosion. But even if you only use oil the clean the bore, it will remove the vast majority of the contaminants. Oil and wipe the inside of the barrel a few times and it will clean a lightly used barrel. But with a heavily soiled barrel I'd still want to use bore cleaner first.
Some areas, like the pivoting extractor, I will disassemble, clean, and relubricate with synthetic grease on a schedule, but NOT add lubrication between cleanings. Adding lubricant or using a degreaser can introduce contaminants inside the bearing areas of the extractor. If for some reason it was obvious that the extractor needed cleaning and I did not have the time or my tools to disassemble it, I would flood it with synthetic oil and work the extractor until no crud appeared to come out and then wipe off the excess. Then later at my convenience, I would disassemble the extractor, degrease, relube, and install a NEW coiled spring pin.