This is an easy conversion. Lubricate the case, resize in 8x57 die, trim and anneal. Fire forming helps but is not essential.
You can use a tubing cutter to make a rough trim, followed by finish trim with whatever case trimmer you have or like.
I have and use Wilson, Redding and Lee case trimmers. Like the Wilson best. Have used this process to make 7x57, 7.65x53, 7.7x58, 8x57 and 308 Winchester from 30/06 and 270 brass.