Repairing bubbled emulsion - which filler?

[MyOldHouse]

Good Evening,
I'm just starting out doing up an old Victorian semi - Walls were skimmed 4 months ago, left to dry 6 weeks then mist coat of contract matt with 20-30% water applied by roller after some filling/sanding where required. Went on terribly - some areas it barely soaked in at all and needed lots of sanding, mixture adjustments and repainting to finally get to a flat consistent finish but it never bubbled at all. I suspect there is something not right with the skim coat. This week I finally applied my first coat of farrow and ball estate emulsion to the wall.

To my horror the last section I did had 3 largish bubbles appear which peeled off to reveal the plaster beneath them (so took the mist coat too). photos of the smallest area attached. I spoke to the decorators I got the paint from who suggested sanding, applying Zinsser gardz then repainting in layers. I couldn't feather the edges of the bubble back as it kept just peeling the farrow and ball off the wall leaving the mist coat so in a fit of annoyance I painted it again - it looks awful. The farrow and ball is really hard to sand back and the edges of the "bubble" are clearly visible - Think I need to fill them then repaint but not sure what I should fill them with. any advice on sanding/filling/fixing greatly appreciated. photo of the terrible paint job that I haven't even attempted to sand back also attached!

 

[MyOldHouse]

probably should clarify - I applied the Gardz as they suggested minus the sanding back of edges, left it the 3 hours then painted over it as the decorating shop that sold it to me advised, no more bubbles but I can't hide the edges of the original area thus me thinking I need to fill it or something as well

 

[misterhelpful]

Try a ready mixed fine surface filler. As Gardz has been applied, there shouldn't be any need to mist coat bare plaster spots before filling. Once dry, sand the filler lightly with a very fine grit sandpaper to help feather the edges. Too harsh of a grit will cause the surrounding paint to scratch away, and may even take the filler off. It's a delicate balance to get it right, but if you take your time, it can be done so well that you should have an invisible repair.

 

[MyOldHouse]

Thank you misterhelpful - will give it a try and see how my amateur skills go at an invisible repair!