I use 1.5 ml of 3% RU a day. Usually in 70/30 Ethanol/PG, but sometimes I use KB solution.
I was heading towards a NW3 fast, with a ton of weightless and sickly hair. I became a solid NW2 with strong hair about a year in and have been maintaining ever since. I've also been taking 0.25mg of finasteride 2-3 times a week. Every time I've gotten lazy with RU the grease quickly returns along with a shed. In addition, my biggest gains came 3 months after adding RU, so I believe it's a heavy contributor.