I use a 308 or 300Sav die to sometimes push the shoulder back first,,but not always.
I find it's needed more on 303 HXP military brass that I use a lot rather than the 30 Krag brass I use occasionally. Heavier constructed I guess.

Otherwise lube it up well especially at the base. Avoid too much lube around the neck or you'll get dents in the reformed neck. One push into the 6.5 die and there's your case but with some trimming to do of course.
An intermediate step into a 7mm die or something else close to that is a good idea but I've been lucky not having any problems sidestepping it (so far).
Some brass may buckle w/o doing that though.

I use 6.5 Mannlicher Schoenauer dies.
The 303 HXP I have to reduce the base a few .000" before they'll chamber. Not needed on the Krag brass (Remington). But I'd rather keep the Krag brass for the Krag as it's getting harder to get now.
The HXP needs an inside neck ream to remove a 'step' inside at the bottom of the neck from the forming process. No reamer available, so I used and continue to use a 'G' drill (IIRC that's the one I keep in the box). It's about .262d and cleans everything up OK.
Once they are 'drilled', I run them through the FL sizer again only this time with the expander plug in place and the necks are ready for a bullet to be seated.
Never had a problem.

No rim turning but I've read where some have had to do that so they'd work OK in their rifle.

220 Swift can also be used if your rifle will work with the smaller dia rim on that case.
The 220 case has 30-06 size rim, the body is about right for the 6.5. Not much trimming after reforming and no neck turning to be done.
Can be used to make 6.5 M/S too but you have to turn the rim down of course and cut the extractor groove out a bit.