My 2p worth here. I personally think your problem is the yellow paint, I believe that its is an oil possibly lead based paint for sealing walls back in the day lol. If moisture comes through it can get trapped behing the oil based coat and cause it to bubble. Maybe scraping back and filling added to...
Lining doesnt need to be plum. I crossline. Do the top 1st, sometimes the ceiling is off so overlap slightly and trim tight. As shedman said take round corners usually about a fingers width but i over lap the otherside and trim tight. Butt each length tight never leave a gap that someone who cant li...
Honestly, there is no cure without stripping the paper. All i can think of for a cheap fix is cut out all the air bubbles/ blisters creases and what not and fill them flat, sand and paint or cut out fill and paper over with a tree bark effect paper and paint.
Most reds, purples and blues have die in them meaning its harder to cover.3 coats should be sufficient. If not try undercoat and 2 coats of white matt. Crowns covamatt is great for this aswell.
I always preffer a brush, Far better finish, Just dont throw the paint on keep the coast even and put a little drop on at a time, Allow about 5 min for runns to occur and then just give them a dab and brush out with a dry brush. Everyone gets runs at somepoint sometims it just fills down the edges h...
There is no cheap fix that i know of. Normal gloss is what you would put in a paint gun so i doubt that would work, There is a samll enamel spray that you can use but its mainly for just the chip its self. If its a small hand sink it may work.
I have never knowen anyone to have used this, Dave could you tell us how you got on with this. Is it really as easy and as good as the advert states. Just so i know weither to give up plastering :o