Programs for reskinning

I've looked in many other forums but haven't had success, i was looking for the programs needed to reskin and where to get them 

https://www.railworksamerica.com/forum/
https://www.railworksamerica.com/forum/viewtopic.php?f=29&t=10403
NSrailfan6130 wrote:I've looked in many other forums but haven't had success, i was looking for the programs needed to reskin and where to get them
ConrailHeritage wrote:I' personally use Gimp 2.6, DXTbmp, RSbintool, and occasionally MS paint for resizing and rotating. (Thanks, buzz)
GIMP 2.6 is free, not sure if it still is.