What is the 'correct' way to lather up shaving cream from a tub please?

[Jakebullet]

With creams I soak a badger brush in a warm cup for 5 mins then pull a fingertip full of soap from the tub and rub this into my face and neck.
I give the brush 5 gentle shakes then start face lathering.
This provides enough soap and water for 4 passes.
For a while I’m using the badger tips to agitate the cream, then I gradually add pressure to the brush on my face releasing the warm water loaded in the brush. After 2-3 mins I have a face-full of great smelling lather and enough soap left in the brush for a four pass shave.

 

[Bengal Tiger]

Dip the wet brush into the tub. One swirl should pick up enough cream. Then face lather. If you need more cream, dip your finger to get some. If you need more water, sprinkle some onto your brush with your fingers. Trial and error and see what works for you.

 

[Happy Jack]

Whatever works for you is best. I would avoid getting water into the shaving cream though; it can get a bit messy.

As others have said, a lathering bowl can be helpful and there's no need to spend a lot of money. Personally I use a small silicone pet food bowl as a lathering bowl. It has moulded protrusions in the base (meant to make pets eat slowly), which really help making a lather. These are also sold as travel shaving bowls at more than twice the price. I bought mine for less than £5 delivered, and they're practically unbreakable. There's many other bowls that will do the job, just grab something from the kitchen to start with.

An almond sized dollop of cream, load your brush with as much warm water as it will take (don't shake or squeeze any water off) and give it a stir. It's surprising how quickly a runny, watery mix will turn into a nice, useable lather:

 

[ShaverAZ]

Many of the "Professional" Youtube shavers soak their brush, then drop it into the soap jar sopping wet. They then slop it around (presumably because they have a spouse or parent to clean up after them) spilling the excess all over the sink or countertop. Keep slopping, spilling snd stirring until you have the proper consistency. This procedure precludes the need for any fine skills, since you just stir until enough soap in the jar displaces the excess moisture.
Folks who are more concerned about making a jar of soap last a little longer, will scoop out an almond-sized dab and press it into the bottom of their bowl then whip up a lather. This keeps the jar of soap dry so that mold or spoilage from storing a closed wet jar of soap is minimized.

 

[DEgeezer]

..........Folks who are more concerned about making a jar of soap last a little longer, will scoop out an almond-sized dab and press it into the bottom of their bowl then whip up a lather. This keeps the jar of soap dry so that mold or spoilage from storing a closed wet jar of soap is minimized.

With a cream there is no need to make a mess. As stated, just scoop out a Dollop, put it in your bowl, and whip up your lather.