1) I just use a tight thong, a size too small. The stretch lace ones work best for me.
2) First I get everything in front into position. Retracted up into the inguinal canals, and stretched out flat along the perineum.
3) Make sure the thong front is covering and holding in everything just right.
4) Then the finishing touch is to haul up on the back of the thong, wedgie-style, to lock the assembly into place. Hold the front assembly in place with one hand while pulling up the back with the other hand. If you've arranged everything correctly, the wedgie does not hurt, there is no discomfort. Then I pull the sides up over the hipbones and smooth them out, which helps hold up the back, which helps maintain the entire assembly.
The resulting profile merely plumps up the mons veneris and you look exactly like a girl.