Well this isn't rocket science, but using filler is one of the basics of model building that can't be underestimated.  Early on, I used old X-Acto knives for applying putty.  This proved to be OK, but the results weren't as good as I can get with a proper putty knife.  The putty knife with the curved blade is my favourite.  For me the curved blade fits more places much easier.  Straight blades are not as easy or forgiving to use.  Not much more to say other than that.....it's all pretty straight forward.  Spend a few bucks on a proper putty knife....you'll be glad you did.

Steve Bamford

Reddish stuff is some dry filler.	I don't use these ends much.