I'm using .25/35 dies to make/load a similar cartridge, the Marlin .25/36.
First, you will need brass. I reform .30/30 brass. Yes, it can be done, but takes a little patience. If using once fired brass it helps immensely if you anneal the brass. Much has been written on this over the years, but it's much easier than you may have been lead to believe. I use a Lee case trimmer shell holder and spindle chucked in a cordless drill. I place the neck and shoulder in the flame of the burner of my gas stove while spinning the at a slow-medium speed. It takes about 7 seconds to detect the slightest change in color of the brass. At this, I dunk the case up to the shoulder in a coffee mug filled with water. The case is then dropped in a container with a towel to absorb any exterior moisture.
2. Important..... Lubricate case necks and shoulders with Imperial sizing wax.
3. Run the dies in about 1/3 of the way into the die, sizing down the neck until you begin to contact the shoulder. Remove the die and wipe any excess lube from base of neck and shoulder. Then run case 2/3 of the way into the die. Wipe again, then finish sizing to set the shoulder to where a case will just barely allow the action to close over it. I loose about 1 out oh 10 cases to folded necks or collapsed shoulders. Not too bad, really.
4. I then trim to uniform the lengths to allow case mouth crimping.
Mike Venturino recently wrote the best article on loading the .25/35 in over 40 yrs in a recent issue of "Handloader" magazine. I suggest you get a copy of it. It will help you greatly.
Lastly, perhaps your greatest challenge will be finding suitable bullets for your rifle
Jacketed bullets are " unobtanium". I have some scrounged 60gr Hornady FP's I've had for decades, intending to eventually shoot through a .257 Roberts, but never did. Likewise, I have several hundred discontinued Hornady 117gr Roundnose also intended for the Roberts and WbyMag.
For the l/a I bought a set of NEI 90gr bullet molds. I've been casting for 4 decades, so a set of molds and Lee .258" sizer die was allI needed.
Good luck on loading for your .25/35. Diligent looking will likely turn up some brass, bullets and data.
It's very rewarding to see those holes appear in the 10 ring at 50 yds when you reformed the brass, cast the bullets, and load the ammo.