I can answer this two ways.
As a Kid, it would generally depend on who was spanking me. Mom was more on the spot, where as Dad would send me upstairs to my room and let the upcoming lesson kind of sink in.
Regardless the procedure was similar in one way. it was always bare butt. There were two reasons for this. The first of which was both my parents thought it was more effective. the other was due to my incontinence, (due to an injury when I was super young) I wear diapers full time (the alternative almost guarantee's continuous infections, but that's besides the point) I don't know how many of you are into diaper play of some kind, but clearly giving a spanking over a diaper is not effective.
So regardless of who was giving the spanking, it was always bare. depending on the time of day (or if I knew I wasn't likely to have an accident) whoever was going to spank me would undo the tapes on one side of my diaper (the side that would be next to the spankers stomach) take me across their lap, then undo the other tape and lower the back of my diaper to have full access to my bottom.
From there it would be the normal pre-spanking lecture. the worst part of this is that my parents expected you to listen. and if they thought I wasn't paying attention, they'd want me to repeat what they'd just said. And Woe to your butt if you couldn't repeat at least the essence of the lecture, it almost guaranteed an upgrade from a simple hand spanking to the back of a wooden spoon or hair brush.
Finally the spanking would begin. My parents didn't give a set number of swats, and to the best of my remembrance, they never went for X amount of time either. it was at the discursion of my spanker. Course Dad was only home when he wasn't on deployment, so for the most part it was Mom who'd be giving me a spanking. but regardless the result was almost always the same. my butt would be a stinging ball of fire and i'd be bawling like a baby. afterwards I'd typically be kept across the spankers lap until i was in control of myself enough that I could stand without needing to be held up on my own feet.
After the spanking (And a spanky dance. Yes. I did that, I'm not ashamed to admit it) I'd be given another lecture, unlike the pre-spanking lecture my parents didn't expect you to repeat most of what they were saying, probably because my folks realized that because you were bawling you probably couldn't remember details that well.
after that, depending on severity of the offence that resulted in the spanking to begin with, I'd either be re-diapered, and allowed to lay down and get control of myself, or I'd end up in the corner, hands on my head for a time out (Which I HATED, full stop)
Then once I was let out I'd be allowed to fix my clothes (this could also be my parents re-diapering me because doing it myself well bawling wasn't always 100% effective) and I could basically do whatever I needed to calm down.
as an adult, my friend (who is really the only one I play spanky games with, for personal reasons I won't go into here) has two ways to spank me.
Now part of me thinks that he is an evil genus, because even though I'm in my 30's, he makes me feel like a 5 year old.
Now, the first way he likes to do is what I call the "Surprise tactic". When we're doing our ageplay thing, he typically will use non corporal punishments for small things (like me not eating my pea's or something for lunch.) He'll typically stick me in the corner, which he knows I hate. But that's not typically the end of it. He'll do it, and sometimes that IS the end of it, but other times, he'll do it and when it's time for me to get my diaper changed, he'll start the change, and when he has my legs up above my head, he'll go "Oh right, You did *insert offence here*" by that point I have normally forgotten about it, he almost always has a brush or paddle in arms reach (even when I try and make sure said weapon of ass destruction (ha ha) Is not there.) so I'll end up getting a brush or paddle across my rump in the diaper position.
Now, I'm not easy to embarrass. I mean it, it takes a whole to embarrass me. but for whatever reason, being mid change (sometimes with a fresh diaper under my rump waiting to be taped up) with my legs above my head, and having to watch as he brings the brush, paddle, or even his hand down across my rump until my butt is as red as my hair... Well something like that is super effective in making me blush.
the other way is he'll wait until after I need a change, (he doesn't hide the fact that he's going to spank me at this one so I know it's coming) then before re-diapering me, he will make me stand up, climb over his lap, and get a regular OTK spanking. Honestly aside from the fact that I know I'm going to get my rump roasted, I honestly prefer this one because for whatever reason in my mind, being spanked in the diaper position is a million times worse then getting an OTK spanking like a 5 year old.
He also likes making me stand in the corner, sometimes he'll even use a marker to put "remove before spanking" on the back of my diaper (Which I do find funny) but that's how he dose it.