IOS-XR BFD configuration guide is quite long. The IGP part is not, but you should understand intervals and multipliers. Legacy IOS BFD configuration is also available, but was lacking sane values for my favourite legacy platform Catalyst 6500 / SUP720.
As a quick start for BFD for OSPF between IOS-XR and IOS see:
Scaling limitations legacy Catalyst 6500 / SUP720-3BXL + DFC: As per very legacy IOS 12.2SXI release notes the scaling limit is at least 50 sessions with 50s intervals. Tough this software release is rather old and does not go into platform specifics. The intervals above do work without any issues from my point of view.