The other thing to remember is that once you start applying dressings, bandages or any other pressure pads onto the wound, never take it off.
Keep adding onto it, or over it.
There are two major reasons for this.
1- if you are lucky and the blood starts to clot, then by removing the dressings will only cause the wound to bleed all over again.
2- the medics and doctors need to estimate the loss of blood to ensure that sufficient replacements are added back into the body. They can use the rags, pads and dressing to judge the amount.
Remember in an attack it will be life over limb.
It is better to loose a leg than a life!! do what you have to on scene to try and help.
To get the full effect of a tourniquets on the femoral artery, place an object under the tourniquet like a pen or any other small hard thing you can find on a boat to increase the downward pressure into the leg.
I would even use a big cable tie if it will stop the bleeding in time.
And remember to panic slowly yourself!!!
Gangrene can be cured- to an extent, but not death.
It is not a nice topic, but one that is valuable in all accidents.