Professionally I don't have a problem pulling a bearing to perform some other service and throwing it back in as long as I was careful with the environment as you say with the wax paper. I pull the outer bearings to change rotors and ball joints. I lay the parts aside in a clean rag and throw them back in to finish the job. Back to your original question. If there are no grooves or spall marks on the old bearing and they weren't growling, by all means clean and repack them. Slight discoloration on the bearings is normal. I just wipe most of the old grease off with clean rags and repack with my hands. the new grease forces the old grease out. Considering how many bearings I've packed, it adds up to several million miles and I haven't had a problem using this method. As someone else pointed out, bearing pre load is what is critical. Be sure to get that right.
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