Pet Rescue Saga Level 534
Target: Save 10 pets
For this level, you can lower the spring (line blaster) to be level with the spiky multiplying viruses, then release the key and blast the viruses straight away.
Then work on getting the pets down.
The paint booster is very useful for painting the same colour over any un-matching blocks that might be holding your pets up from dropping to the bottom.
The level can also be played without destroying the viruses immediately, they too can be useful for clearing large amounts of blocks.
The paint can also be used to break the diagonal pattern the virus spreads in.