repotting oncidium in bloom with new growth

[Mo Boggie]

Hi. I have a root bound oncidium in bloom, with new spikes emerging (sherry baby). I just noticed some new growth that may be bulbs emerging. Should I wait for all the blooms to fade before repotting? Also, I can't tell what type of potting mix it's in. I'd have to remove the orchid to find out what it's in. Seems like it may be a course material like hay with dirt on top. What should I repot it in. Should I attempt to put it n s/h? BTW I have a long history of overwatering. Thanks Mo