I changed my faction from Dead Orbit to Future War Cult on Thursday 2/11/16. Hit Xur on Friday and hit rank 8 from what I had in my inventory. Grinding all week for items then hit up Xur again Friday 2/19/16 to reach rank 16. Xur again this morning Friday 2/26/16 and hit rank 25 with the FWC. Completed ranks per week: 8,8 and 9. I used all of my strange coins on heavy ammo synths from Xur, traded ether seeds for Heavy ammo synths at the reef and purchased a ton of weapon parts. *Edit* I also traded black wax idols for heavy ammo synths from Eris, it was only 25 of them though. I bought a few pricy items during this grind also such as the $17,000 ship from Petra, "donated" $15,000 for the only exotic I don't have the chaperone, and bought all $12,500 worth of gunsmith packages. That $44,500 would have added about 3/4 of a rank extra with the use of weapon parts. *edited* I increased my faction from 0-25 in two weeks but I would say using this way it's about a 3 week grinding process.