Joint filler - coverage

[dangti6]

I have nearly finished putting up a 40sqm ceiling. 

 

I used 9.5mm sheets (to match existing, and it's only a garage), straight edged (merchant doesn't supply tapered in 9.5).

 

Therefore I have a fair amount of joints, all butted. 

 

I am looking at taping and filling. I bought some Gyproc 'FibaTape Xtreme' mesh tape as it's supposed to be nice and sticky. The existing section of ceiling boards are fibre backed paper taped. Would you remove the paper and replace with the mesh or just fill over the tape? It's quite well stuck so I am tempted to leave it unless renewing with FibaTape is likely to give a better chance of a half decent finish.

 

Filler wise, I am looking at using this Gyproc stuff.

 

British Gypsum Gyproc Joint Filler 12.5kg | Wickes.co.uk

 

No idea how far this stuff goes when mixed. Potentially how long is a piece of string, but how many bags would you grab as a starter to give you decent chance of having enough? 

 

Does the filler and or plasterboard need sealing before painting over? 

 

I have considered having it skimmed to save the effort, but it's a garage and I need to reign it in.