Couple ways
On the froward drum you can use your finger and do some of the resizing then lube the center support that it goes in and it has a tapered opening. With some caution you can force it into the center support. I have also used electrical tape. On the center support I use a strip of .010 shim stock long enough to lap over a couple times (the width of the 3 seals) and use 3 radiator clamps to pull in down. Best of luck.