Direct fired brew kettle insulation ideas?

Hi everyone,

After having recently bought a huge 100L pot for a community BIAB project, I am now trying to figure out how to heat this thing without breaking the bank on LPG and waiting for ever for the thing to heat up.

This topic has come up in the past on this forum:

http://www.forum.realbeer.co.nz/forum/topics/insulation

but little guidance or experience has been provided.

I do have an idea but am curious what other people are using for their direct fired mash tuns / HLTs / or brew kettles if anything?

My thoughts, which I'll put out their for peer review, are to buy some fibreglass fabric (like at the boat shop), borrow my wife's sewing machine, and make a quilt out of it with low-dust pink-bats insulation on the inside.  I recon this way one might be able to have the pot insulated while firing and thus saving on gas, money and time.

All ideas, criticisms, insults are appreciated.