If you are referring to the type of bolt rifle shooter who takes the rifle down from his shoulder to cycle the action between shots, then a bolt rifle is "very slow". However, those of use who have shot with bolt rifles competetively can tell you that an experienced shooter can cycle the action by the time he has recovered from recoil without ever taking the rifle from his shoulder.

As far as a hammer double rifle is concerned, cocking the hammers is as easy as cocking the action of a non-self cocking action like the Krieghoff, which has no safety, but depends on both barrels being cocked by means of a thumb operated slide immediately prior to firing. Easier, actually, since you have the option of cocking one hammer at a time,

Underlever rifles were made in two different patterns, the Jones action, which uses a rotating lever, and the Jeffery type Under Lever Snap Action, which uses a lever which is pushed forward from under the trigger guard. Both are quite strong, but the snap action is easier and quicker to use.

Here is what John Taylor had to say about hammer doubles in his book "African Rifles and Cartridges":

"I am very fond of the double hammer action because of the absolute silence in which it can be loaded and cocked. I know of more than one man, sitting up at night for man-eating tiger, who scared off his beast by the click of his safety as he prepared to shoot with a hammerless rifle. If you draw back the trigger at the same time as you draw back the hammer on a hammer rifle and then let the trigger go, you will have cocked without a sound of any sort. Then there is the delightful eas with which the breech opens; powerful double rifles are fitted with extra powerful main springs to obviate the possibility of a misfire; those springs have to be compressed as the breech of a hammerless action is opened and the locks cocked. There is nothing of that with the hammer rifle—you cock with your thumb, one lock at a time. I would happily finish the rest of my career with nothing but best grade double hammer rifles. Incidentally, such weapons can occasionally be picked up secondhand at very low prices—not becuse the hammer action is no good, but simply because fashion favors the hammerless. If you get such a chance, provided the weapon is in good condition, you need not hesitate—it will satisfactorily answer any questions you are ever likely to ask it."