Brownell's Chamfering Tool Kit has everything you'll need (except the lapping compound, which is separate).
I liked the 5 degree cutter when I did my 357s.
Also has the facing cutter to square up the barrel's breach extension if you need.
I bought a second pilot bushing for each caliber too. I found it beneficial to have one pilot near the breach end & the second one near the muzzle so you don't have to constantly monitor that the muzzle's center guide is staying in place while you're cutting.
The kit's not cheap but worth it though if you'll eventually be doing more guns.
You can save some $$ by using the mouth of a sized 38/357 case to use as a plug gage. (The max FC mouth diameter shouldn't be over .377", which the case's OD" will be close to.)
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