What's the difference and advantages of Tamiya's Extra Thin Cement over its regular liquid cement counterpart? How about it vis-a-vis other brands, such as Model Master (the one that comes with the needle applicator), Humbrol, etc.?

I have used both but find that teh fine stuff dries really quick so you usually need to add more coats. It's good for getting into tough little areas, flows well but be careful might flow unto model. i use the regularstuff for big parts and stuff that need to stay wet for a while as I put pieces in place.

To soften the plastic to give the impression of "rough metal", I was given the advice to use the extra thin glue.

AS the name says, it's so thin that's it's ideal for applying on seams to enable it to weld together. You can tell from the brush applicator as opposed to the regular cement.

Here's an inexpensive way to refill your bottle rather than having to buy another one. Refill it with a mixture of PU (Polyurethene) Reducer and Choloroform (no kidding).

You can get the Reducer from your nearest hardware or paint store. Choloroform, head for Mercury Drug. Caveat: Tell them you are gonna use it to cement acrylic boards. The staff will always ask why do you need chloroform.

I tried it myself and I swear it works as well as Tamiya's original formula.