I've been using Vagifem for years and it's made a huge difference to me. I'm 51 & started taking it before my periods had completely stopped. I would take it while bleeding as long it wasn't heavy.
I don't find it ever leaves residue.
I would avoid using it before sex.
I don't take HRT at the moment.
The reason I started it was terrible vaginal pain all the time. I had been bleeding slightly after sex for a long time & having frequent UTI's as well. All symptoms of vaginal atrophy I suppose. After a few wks it stopped all that. I often forget to take it twice a wk tho & just take it once, but still no return of previous problems. Hope it helps you too