Treatment for ECKEL Small vocal isobooths -600lbs 3'x3'

[mrm]

Sure learning a lot about sound in this forum!

SMALL SOUND ISOLATION BOOTH
At our Habitat for Humanity used building materials store, I bought an old
Eckel Sound Isolation booth (AB 200) - it weight 600 lbs. - PAID $150.
New, in Canada, these are $5,500

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I do know there is a difference between sound isolation and sound treatment.
I also know from this forum, that it is a very tiny sound booth, and very far away from the ideal large sizes,
although I see many people using small vocal isobooths for voice over on the Net.

I'm going to use it mainly to learn about sound,
record foley, voice over - and to share with my students
who are doing their first recordings.
(I added wheels to it, and it can pass through doors at school).

I've recorded voice samples in the room, and my guitar so far.
The recordings are clear and room seems quite dead,
guitar bass notes sound good, but are very noticeable

I read: "Small spaces (vocal isobooths) tend to be boomy; bass traps mitigate this."

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I'm wondering how to treat the room.

ADVICE please

Here are things I want to try:
(I enjoy building things DIY, and experimenting, and studying audio and theory)

- drape "moving blankets" on the walls. (walls are perforated steel, no echo/reflection is noticeable now)

- making a TUBE bass traps and hang in one corner (I've read a lot about bass traps on this forum)

- I removed old carpet and installed OAK flooring.

- acoustic foam on ceiling.

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Any advice would be appreciated, I'll post pics and samples when I finish fixing it up.

Thanks,
Rob