Probably depends on the map. I had a lot of trouble with it on downtown, till I realized that pretty much as soon as you hit the main route through the highstreet, there's a van. You can squeeze between the wall and van and easily do all of your handcuff/flash/dildo missions there.You could turn it to day and search for two people talking, you can go behind one of them and do it on them. It's one of the easiest mission to do.
Handcuff to object is definitely one of the most hardest thing to do in certain maps.
Hell, there's a spot right next to it where NPCs stop to smoke or look at their phones, but they never ever turn their heads to the side, so you can even do all of the missions that require you to be near people too.
For the apartment block, I used stairwells for most of it.
Although tbh the whole zone seems pretty empty. I only had to deal with one or two people.
I will say though...

The developer has a pretty odd definition of the word 'naked'
She's wearing more in this screenshot that she was when the game started!
It's the same issue the first game had, but even more pronounced. The only real gripe I have with the game, aside from the missions being generally repetitive.
There's enough unlockable costume pieces for you to assemble multiple full outfits. But the developer doesn't really know how to handle you having a T-shit and a skirt, or jeans, or slacks, or a bra. So the game just ignores it.
The only clothing that the game will recognize is the black coak that she starts with. Nothing else counts as clothing. Obviously this means that you'll 'get caught' if you walk out on the street dressed like a nun, a ninja, a succubus, a schoolgirl, an office-worker, ect.
But worse that than, it means that you can't use any of the flash commands in those outfits either, because you are 'already naked'
I'd love to see Manaka flashing in the schoolgirl outfit, pulling her skirt up or her shirt open. And a lewd nun lifting her habit would be great.
Alas, it's not to be.