Putty question

Hi, recently i started using putty for some mods i do on my models (i'm quite a beginner on modding models) The brand of putty i use is called Mr.Hobby-Mr. White Putty. First, is this a good brand to use, or are there better choices out there? Secondly, i found out this kind of putty won't fully harden until around a week later or so, is this normal? My last question is, besides filling in holes/spaces what else can putty be used for? Can you make spoilers out of it? would it be strong enough?
Thanks

Um.... well i've never used Mr.Hobby-Mr. White Putty so i can't give you any suggestion on it.
I use Tamiya EPROXY putty there are 2 type ones fast dry ones slow dry bu they kinda work teh same. From my expereince these dry in liek 6hrs. YOu can sand then and do what ever after 6hrs.
To make spoiler i think plastic sheets you get from hobby shops will be better and alot easier. But putty i don't knwo never tried other guys here shoudl know.

Good luck :D