I've been trying out using soap to get lather. My gear is an old onion soup mug as scuttle, a cheap Wilkinson Sword boar brush from Boots, Geo F Trumper sandalwood soap, very soft water.

My routine is as follows:
Soak the bristles in warm water in the mug while I shower.
Tip out the water, leave a couple of drops in the mug.
Shake out the brush pretty thoroughly.
Put a little water on the soap, build up a bit of paste/thick looking lather on the brush for a minute or so.
Whisk the lather up in the mug for a minute or two and apply it to the face.

The problem I have is that the lather just doesn't last on the face, I apply it, then strop the razor, by the time I'm done stropping the lather is all gone and I have to keep reapplying frequently. I just can't seem to get a nice thick lather that sticks around, can anyone advise me on where I could improve? Is it the cheap brush? Not enough water? Soap brand? I'm intending to upgrade to a nice Thrown in Stone Scuttle come birthday, but I feel the scuttle has probably the least impact on this process, am I wrong?

Thanks.