I was thinking, instead of buying rather expensive zimmerit and tools for it, could one just heat a flathead screwdriver, and indent the plastic of the model itself? I mean, what advantages and disadvantages would you have with it? Thanks for your time.

I did it once in one 1/72 Elefant and it is quite tedious, it took forever, and I used an screwdriver for watches. What you could do is to make it from green putty, really cheap.

This Idea is an alternative to a popular zimmerit techniqe used for years. Instead of a heated screwdriver a Hot knife with interchangeable heads is used. The results look ok but in my humble opinion putty is still the best looking zimm. Just my two cents.
Cheers,
Bryan

How could I use the green putty? Thanks for your time.

I made this simple sketches to help you out:
First you brush on the putty, don't use your new winsor&newton brush, it ruins it. Try to lay it out as thin and even as possible, if there is any detail not to be covered then mask it.
Then you brush on acetone and smooth the putty out, remove all excess putty.
Then the zimmerit pattern is formed, I use a screwdriver and do it from the top down, some reference to see how the pattern goes
practice makes perfect.

MEBM -

I'd go with DRAGONSLAIN's approach, though I like to use the "zimmerit" tools like Tamiya offers. This is an added expense, but the results are worth it. The major problem with the older technique of using the heated screwdriver directly on the plastic is the danger of errors which aren't forgiving to the model. Green Putty can be removed, if necessary, without that kind of damage to the model. Just my preference,

Blade48mrd

You could use the elmer's interior wood putty. Its cheap, a plastic bottle will cost you just $1. I already tried using it on my panther....its easy to apply and easy to remove (if you make a mistake or does not like outcome)... I used the x-acto blade to produce the cross ridged pattern....hmmm just don't apply it to thickly like what i did (my first time to use it.... :-) )....

You could see the panther in my gallery...

hope this helps

Cheers