You don't need snap caps to dry fire a center fire rifle, but use 'em if you got 'em.
In my experience the following is a good way to ward off flinching.
Mount a target somewhere indoors (so you can practice at night). This target may be a little blurry through your scope because most centerfire scopes have a minimum parallax set at about 25 yrds.
Dry fire on target (offhand), concentrating on crosshair movement. Repeat night after night until you can achieve a smooth let off and FOLLOW THROUGH with minimal cross hair movement...and until you can transfer this feeling/sensation/sound to releasing the trigger on a live round (not at the same indoor target, of course
). Repeat as necessary.
Practicing with a pellet gun with a heavy trigger and stout come-back (like a RWS 48), is also good anti-flinch medicine. You must really hold, squeeze and follow through on these sobs to shoot good groups,