Manual machine, presumably with acme screw drive? Conventional mill, do not climb. As to feed, consider how stiff/stable the machine is and find the balance. Whatever you do, don't rub, maintain your cut.
Good flow of coolant will help, and I'd use a face shield as well as safety glasses.
[To be honest, I'd probably not try cutting Inco 625 with a saw that big on manual equipment]