Like Mark said, there are resin aftermarket Zimm sets being sold for $20-$30 and they really look great.
If you really want to do it yourself then here's the helpful information. I used the putty to create Zimm on old Tamiya Pz IV kit and I have to admit it was fun! You will need a tool or you can use one of those saws. I used this Zimm applicator set from Tamiya...
And I used 3M Glazing Putty. It has fair drying time for about a minute or so. You can buy it at auto shops. Be sure to go for blue or white because they offer longer drying time. I was told blue has been discontinued so white was the best alternative. I think I paid $17 but the tube is HUGE and it will last forever hopefully.
My first attempt applying Zimm and it wasn't that hard. Just take your time and do small sections at a time.
Result...and it brought home an award from model show. You can do the same!
I would do it again in a heart beat if time isn't a factor. Next time I want to buy the Zimm tool set from Trumpter that comes in rollers.
Hope this helps...