There are two different products, one called Green Stuff (**LINK**) which I think would be the two-component epoxy putty mentioned by Tim. It does indeed have that in common with Milliput that it is two-component and epoxy-based, but I believe that it has different characteristics. There's some in a drawer in my workshop, but I've yet to use it, so cannot comment from personal experience. I know, though, that it is popular amongst the figure modelling crowd.
Then there's also a one-component hobby purpose filler from Squadron Products called Green Putty (**LINK**), which I've never used or seen, but suspect might be popular with plastic modellers, who I think is the primary community served by Squadron Models.
As for whether the Dumas USS Whitehall kit is a good (re)starter project for you, if you have lots of time and patience, why not? There's really only one way of finding out … and even if a first project does not necessarily turn out as one saw it in one's mind's eye, the process is likely to be mainly enjoyable with plenty of opportunity to learn.
Again, if you have time and patience, you should be fine! Read the instructions through several times, while looking at and handling the parts described, and then have a good think about each step before you start work on it. Build in your mind before you build with your hands. (Personally I love to think things through while waiting to fall asleep at night.) If you feel unsure, or don't understand, read and think again, or do additional research on the 'net or in books (your local library will not be likely to have all that much on their own shelves, but it is surprising what you can get through inter-library loans) or ask questions here or on other fora. Measure twice before you cut, and if you're not happy with a result, try again until you are. Because in the end the only two things that count are that you enjoy the process and that you are happy with the result. If other people like what you've built, too, that's nice and a bonus, but the only one whose opinion actually counts is you yourself.
Good luck and have plenty of fun!
Mattias
Edited By Banjoman on 19/07/2018 09:39:17
Edited By Banjoman on 19/07/2018 09:40:31