I'm sure I'll take another leg striping from the resident self appointed mall cops... but I'm getting used it it. :o
The Hornady factory match load for their 285 grain bullet is also Retumbo, at Hodgdon's max of 94 grains (work up to that charge)... but yes, it's in Hornady brass of course.
The Lapua cases seem to want about 2 percent less Retumbo than the Hornady. That should put your OCW at 92 grains even.
Work up from 89 grains and you'll be safe. But see if I'm not right, that 92 grains is where you're gonna want to be with the 285's in Lapua brass.