Although there are bound to be other ways of using this filler I thought I would share with you how I use it as it's actually pretty good stuff and often more readily avaible.
Squadron putty comes in tubes that has to be squeezed out like toothpaste.
I have two sorts Red(which is Fine and is actually light grey in colour) and Green(which is Coarse and well, Green).

The tools you can see are a set of cheap wax sculpting tools and as they are made of metal, cleaning any excess off is as easy as wiping it off.
The model I will be demonstrating this on is my Beaufighter that is in the WIP section.
Here you can see the gaps on the upper and lower parts of the join between the wing and the fuselage


First of all to protect the surrounding area from the metal tools, cheap masking tape was cut into thin strips and placed around the gap to be filled. By doing it this way it reduces the amount of filler to be removed and also protects any surrounding detail from excess filler such as panel lines.


Now your ready to begin filling.
Chooseing what to use to apply the filler depends on the area thats being filled(use your best judgement on this one).
When applying the filler make sure you apply gentle pressure to make sure the paste is actuall going into the gap and not resting on the surface. I tend to do a little bit at a time making sure it's in the gap.
The putty takes 30 min to dry but I like to leave it a bit longer to fully set.

Now that it has full set carefully remove the tape and you should be left with a thin band of raised putty that that can be sanded down. I'm sure I don't need to remind you about health hazards when using this stuff as you read the label,right?.
But there is another way and this involves using nail polish remover. I use this stuff from Boots it cost 99p for 250ml.

The important thing is that this contains Acetone that wont attack the plastic unlike Cellulose Thinners that will. What you do is dip a cotton bud into the NPR (Nail polish Remover) and gently brush the putty forwards and backwards. A recation happens and causes the putty to dissolve slightly. Changing the cotton bud often and dipping in clean NPR wil eventually leave you with a smooth join. Any excess residue from the tape can be removed with a cotton bud diped in White Spirit.
Right, now a bit of advice about Cellulose Thinners I'm sure that there are some modellers who can use this stuff and believe me it does work a lot faster, but using NPR is much gentler and much more forgiving to a cack handed modeller such as myself. Mr Jynx.