Adding (At least) a Stabilzer to a SWK Economy Wool

[Mathew MacKillop]

Greetings Noble Rabble,

I am hoping for some advice from our resident pros, be they professional kiltmakers or "mere" hobbyist, I won't complain!

I have a Stillwater Kilt Economy Wool (Black Watch, though that makes no difference in this context), and though I truly love the thing, and plan on wearing it AT LEAST as often as pants (will need to wait until I have more kilts for full-time wear; it would be noticeable and frowned upon if I wore the same one every day). These kilts have Zero internal structure, just 5-6 yards of wool, straps, buckles and liner that is only sewn down at the top.
After reading a few threads here, it is becoming apparent that I may need to add in the lacking structural reinforcements if I plan on wearing this kilt often and having it last a long, long time.
However, I have an extremely limited budget (as in, if I can spend nothing on this it would be for the better). Lucky for me, I have several kind lady friends who are more than competent with needle and thread, so the labour will cost me only a few bottles of beer or a bottle of wine.
Now, there are sufficient threads in existence already that the how-to of adding a stabilizer and interfacing should not be an issue. The materials, though, and the necessity of the interfacing, are the intended subjects of this thread.
Considering that I am not dealing with 8 yards of wool, is the interfacing necessary, or will just adding a stabilizer do the job?
What readily available materials can I use for these? I could purchase hair canvas for the interface if needed, but I need such a small amount that it seems silly to purchase the minimum yard of fabric to do this. What should I use for the stabilizer? Are there any materials I am likely to have lying about good enough (old jeans, bed sheets, t-shirts and dress shirts, etc.)?

Thanks in Advance!

Mathew