EasyFill in a Caulking Gun or Proprietary Tube Filler

[FozzieBear]

Hi All,
I have just had some new UPVC windows fitted and need to make good around the frames which don't exactly meet the old plaster line. There is also some damage to internal plaster where straps had been used to fix the old windows in place.
Yes the fitters will make good but they just use decorators caulk for smaller gaps and upvc cover strips for wider gaps and I want to replace the crisp clean plaster line finish I had before.
For the narrow gaps I can use a pallet knife, but wondered if anyone had success using EasyFill in an empty caulking tube to penetrate right into the gap. I assume I may need to use the standard EasyFill 60 to avoid it setting in the tube before I had finished? Alternatively I could buy a grouting gun to do the same thing?
As an alternative, are there proprietary fillers in caulking tubes that go hard like gypsum based fillers like EasyFill that might be an alternative. What I like about Easyfill is the easy way it sands and the smooth finish you get afterwards.
I will run a small bead of decorators caulk between the wall and frame afterwards the assist painting.

 

[Wayners]

Masking on window frames to keep clean.
Lash in joint watered down PVA to bind surface.
Toupret filler.
Sand
Paint.
Fine line of caulk around window
Second coat of paint.

 

[FozzieBear]

Masking on window frames to keep clean.
Lash in joint watered down PVA to bind surface.
Toupret filler.
Sand
Paint.
Fine line of caulk around window
Second coat of paint.

Many thanks @Wayners . Any particular Toupret filler. They only seem to do Fill-Flex or Fibacryl in a gun tube both of which are flexible fillers. Some of the gaps are only 3mm and difficult to get filler in with a pallet knife hence Grout Gun?

 

[Wayners]

I use tx110
Standard is fine

Even at 3mm seal with PVA and fill it will be fine