Igor Maslennikov, director:

The scene where the Hound attacks Sir Henry was also difficult. The dog’s owner doubled as Sir Henry. This time the dog did recognise him and wouldn’t attack him so the director said they had to make the dog angry. The prop master loaded a rifle with bubble gum, but the casting specialist, a kindly lady, made a terrible row, saying that it was barbaric. The director agreed to try it on himself first, and when a bubble gum bullet hit his leg, he shrieked at the top of his voice. The bullets were cancelled.
As a result, in the scene where the Hound is shot from the guns, it was actually a piece of plywood pulled out from under the dog’s feet so that he stumbled.
By the way, the dog had a sweet tooth: he ate Solomin’s cake with the box it was in. (Source: 221b.ru)

Concept art by Igor Maslennikov
PS I came across an interview with the director of New Russian Holmes where he explains his take on the Canon and the choices he made for his adaptation. If anyone's interested, I can translate and post it later :)
Shooting the part with the Hound was a terrible hassle. At first we decided to daub the dog with phosphorus as Doyle had written. We consulted dog handlers about it, and they said we were crazy because it would be harmful for the dog’s power of scent, no dog owner would allow it, and besides the dog would lick the substance off.
Then we thought about using blue screen for special effects. The dog’s owner was dressed in a special blue costume too. The dog didn’t recognise his owner in that weird attire and attacked him. The man was taken to the hospital while we had to brainstorm again. Then someone from special effects suggested that we try Scotchlite tape which is usually used for traffic signs to make them glow.
We obtained the tape and plastered it on the dog. The result wasn’t scary at all, but rather funny: it wasn’t an eerie night monster—it was a character from Brazilian Carnival. We took the tape off and made from it a vest and a mask.

The scene where the Hound attacks Sir Henry was also difficult. The dog’s owner doubled as Sir Henry. This time the dog did recognise him and wouldn’t attack him so the director said they had to make the dog angry. The prop master loaded a rifle with bubble gum, but the casting specialist, a kindly lady, made a terrible row, saying that it was barbaric. The director agreed to try it on himself first, and when a bubble gum bullet hit his leg, he shrieked at the top of his voice. The bullets were cancelled.
As a result, in the scene where the Hound is shot from the guns, it was actually a piece of plywood pulled out from under the dog’s feet so that he stumbled.
By the way, the dog had a sweet tooth: he ate Solomin’s cake with the box it was in. (Source: 221b.ru)

Concept art by Igor Maslennikov
PS I came across an interview with the director of New Russian Holmes where he explains his take on the Canon and the choices he made for his adaptation. If anyone's interested, I can translate and post it later :)