I personally wouldn't do it immediately after shaving, although I rarely shave to the skin, maybe 3-4 times a year. except I do have the bakblade off amazon and I trip the back every 2-4 weeks. I still feel like it needs a few hrs before I'd want to put the topicals on.
People do say the idea of localized impact of most of our TDs is a silly notion, but I feel like ultra hard and dermacrine left my traps sore after a couple days of application there, sorta like a stiff neck but not in a way that left me unable to move. just sore.
I don't like applying to my feet unless I have a LOT of time before putting on my socks to make sure I get full absorption. I have been using more of my upper and inner upper arms (biceps and triceps) first lately, since they're my least hairy areas, then shoulders, then traps. If I do use the tops of my feet...i admittedly will often use one extra pump of whatever I'm using in case any is lost on socks.