All footage of the Red Ranger training by himself is new footage.
Here's new footage of Horn
Here's new footage of Horn with the Transdaggers

Here's new footage of Horn by the Weapons Dome
Here's another new shot of Horn but this time he's in the Weapons Dome
These shots
are the start of Sentai footage.
These shots
are new because of the weapon he uses in Sentai footage.
This shot is back to Sentai footage.
This Blaster that Horn is using as seen here is newly created by the Power Rangers crew since in Sentai footage, he was using a Rifle or a Machine Gun type of weapon
It then cuts back to Sentai footage of the Red Ranger sparking up.
This shot of the Blue Ranger is new footage
Here's new footage of Horn with the Red Ranger
Here's another shot of Furio with Horn with Horn's jacket being opened in order to show up the 5 Transdaggers
Here's new footage of the Rangers with their Transdaggers
Here's new footage of Red with his Transdagger
These shots
are back to Sentai footage.
Transdagger Weapon Mode attacks are a case of spliced footage, they do the attack in Sentai footage but then the Stingwingers take the move in their American footage.
This shot is back to Sentai.
Most shots of Horn that feature him holding a Blaster-like weapon is new footage however the shot in which he takes a blast from the Green Ranger's Transdagger is actually Sentai footage, they forgot to reshot that shot. Oops.
These shots of Horn are also new footage:  
Horn's drinking of his green liquid then cuts to Sentai footage of him growing.

Sentai footage comes from Gingaman Episode 5