This is a 100% beaver from the Mill Whse and it was great felt. Very thick and tough to block. I got a 5 3/4": crown and a 3 1/4" brim before the curl on a 59cm sized hat. Their 50/50 blend is great as well and he should have his next stock sometime this month.
The customer service from Mill Whse is superb. But yes his stocking is hit and miss. The Granite is a great colour. When he gets in stock I place an larger order to tide me over is stock outages.
He has said he makes very little money selling small quantities to individual hat makers. He does a lot of business with larger hat manufacturers. He ships into Canada I think it is for the Bollmann Hat Co. as well as others
Yes, I love working with leather just don't have much cause to do so. Beaver is great. I wet blocked this hat as it was so thick and I could not get the water to drain out of the crown through the felt. It was damn close to water proof. I imagine eventually it would have seeped through the felt but it would have taken a long while to get there.
I have never had that much of an issue blocking a felt. Even 220 gram western weight. Yes, I have to muscle it but with gloves, a hand steamer, a puller downer and then a pusher downer with the blocking springs it does not take too long. The hardest part with the heavier western weight where I need to steal brim width to get the crown height is getting the blocking spring over the brim break. But again a good pusher downer and the blocking springs and determination it doesn't take too long. It is just hard on my arthritic hands.
You need a separate one for each block size. They come in centimetres. The blocking springs and a good pusher downer has helped me a ton. That and lots of steam.....I use my Jiffy Steamer for a good general steam saturation and then I use a handheld for spot steaming areas as I do the blocking.
Yes, they do apply pressure and leave a mark on the felt but in the end they produce the exact measure you are seeking. They don't slip and they really help if you are trying to steal crown height from the brim width. It is much easier to push them past the factory brim break in the felt.
Yes, I match the blocking spring size to the block. So my 59cm blocks get 59cm blocking springs. And yes they hold very tight but being silicone they slide easily down the felt.
No just the felt with the block still inside. I remove the blocking spring at that point as it has done its job. The felt is dry and I use the plywood as a press to flatten the brim and if the felt crown is less than the full 6" I use the correct thickness of plywood so the felt/block sits flat and I can iron the brim and set the brim/crown break. To set the brim/crown break I need the block still inside so I have something for the tollicker and curved iron to set against.
Alden 403 Moc Toe Boot - Brown Chromexcel - $680 The classic "Indy" style Alden Boot in the classic Horween brown Chromexcel. 
Grant Stone Diesel Boot Dark Olive Chromexcel - #395 Goodyear welted, Horween Chromexcel, classic good looks. 
Himel Bros. - The Ross Mk. 1 Leather Jacket Classic D-pocket motorcycle/aviator style jacket.
I have a number of work stations 2' x 2' square tables. I use one of the 2'x2' plywood sheets with the holes cut for the block over top of the blocked felt then clamp them to the table squeezing the felt between the two. The blcoking springs are used instead of the blocking cord. They are easier to push down the blocked felt and I don't have to be concerned about the 'slip knot' slipping.