You have to wait until they're deeply asleep, and it helps if they fallen asleep next to you, so you don't have to sneak up on them. Mine conveniently uses my desk as a favourite sleeping spot (inconveniently most of the time).
Also, you have to have them curl up on the right side, as it's impossible to turn them over without waking them (mine, at least).
The groin tangle was obviously trickier, but I was able to 'get in there' during a tummy rub session - these can go either of two ways; either it turns into playfight, where he attacks my arm with claws and teeth, or where he luxuriates in tickllng bliss.
Fortunately, it was the latter. I had to turn my arm around so I was tickling his tummy with my forearm, and his chin with my elbow. and then get to work on the lump.
I don't know about superhero - I felt more like I was trying to defuse a ticking time bomb.
On Sundays, he's called 'NotNow'.