Today I’m performing yet another upgrade on a 4500 6L-e switch (to 15.2.2E8) and i’d like to recommend an excellent video going thru all the steps on a 4500 with one supervisor and then with two supervisors (not much difference here other than: redundancy reload shelf to reload both sups simultaneously rather than one).
One caveat is that you cannot have slashes in the boot system command. This is the only way you should do it:
boot system bootflash:cat4500e-lanbasek9-mz.152-2.E8.bin
If you use slashes, the supervisor will go to ROMMON and you will need to call an onsite person to help you. A boatload of fun.