To achieve controlled braking, you should use both the front and back brakes, and sit well down on the saddle, putting your weight over the back wheel to stabilize the bike. If you feel the bicycle skidding, release the brakes a little before re-applying them. Feathering is also useful on long descents when continual pressure can cause wheel rims to overheat, glue on tubular tires to soften, and tires to burst. On wet roads, feathering helps to dry wheel rims. Avoid cornering and braking simultaneously.
Bicycles take longer to stop than cars do.
Bike brakes take longer to work when the wheel rim is wet. Brakes work far better on aluminium alloy rims than they do on steel rims. The best brake pads to use in wet and dry weather are synthetic. Though rubber brake pads have a fair grip on aluminium, they skate over wet steel and result in stopping distances that can be four or five times as long as you'd expect in dry weather. If you get oil on the rims, you should get off and remove it before going on.