Specific underwear definitely helps. Like, doubling/tripling up on basic panties can also sorta work, but still not as good things meant for it IME. Unfortunately, they don't come cheap and YMMV as usual...

Grower priviledge~ The tucking panties do most of the stuffing work. They're not small, they're like boy shorts. They're tight and firm. You'll figure it out, I literally just bend the whole package back underneath near the perianal zone. Try some stuff and see what works.