I had the same issue but here is my solution
1. Make a gaff from a pair of tights (Panty Hose)
to do this; do as follows
Cut the waist band from a pair of tights.
Cut a 10" length from the thigh part of the leg
open this up and thread the waist band through the leg
2. Send the twins home
3. pull on the gaff and pull it tight over the old man allowing the the skin from the sack to hang either side
4. Wrap the skin over the old man and pull on your knickers, tight ones are best
And there you go tight trousers, jeans or even skirts and dresses no problems.
my old man shrinks back to nothing during the day so no issues, if you do need a little bit more support then you can use and elasticated head band and thread another waist band through it and pull that tight over him, this can give the look of the labia through you underwear and even tight trousers, jeans.
Hope my instructions are good enough, demonstrating is easy than typing it out
C