1) dont try to shoot them as fast as jacketed (until you are advanced in their use)
2) very often you need a cast bullet several thou' larger in dia. than the typical jacketed bullet for the caliber. So, where a .357 jacketed bullet will work fine, you often want a .359 or even bigger for cast. This is because any propulsion gases getting up past the lead alloy base into the rifling will gas cut (like a cutting torch) the bullet destroying accuracy and causing leading. Jacketed bullets can resist this even though they may (and often are) actually too small for the bore/groove dimensions too.
My rule of thumb is to use as large a cast bullet dia. as comfortably fits a fully fire-formed case mouth as possible and still chambers up and extracts cleanly. You are 'fitting' the bullet to the all important throat, which hopefully is at least groove dia. of the barrel or a tad larger. I used to slug barrels and throats and work a new gun up, for some time now I just do what I say above and it almost always starts working right off.
3) most die sets are designed to load jacketed bullets, so they undersize the neck and button it back out or expander plug it out to jacketed bullet dia. (actually a bit under for proper neck tension). Real die-hard (oops, pun....) cast bullet shooters often get/make expander plugs a bit larger just for lead.
The important thing for you at this point is to know that if you fully resize a case and force an 'oversize' lead bullet into the neck that you are 'sizing' the bullet down a bit, thus undoing some of your proper fitting. Best bet may be to not resize, just decap, recap, bell the case mouth a tad to start the bullet, powder charge and seat a bullet.
