Hi, there are many other great forums where most of these topics are discussed. I will not compare oils, I only tried one the Revolution BioBooster, which I liked, the effect was there for 4-6 weeks depending on the rubber, but in case of older (1 year) red sheets, they melted.
Most people apply booster with a paintbrush, but I use a sponge. If it is inbuilt use the sponge.
So most times people apply the oil to the sponge. There are methods and preferences about the exact amount. I usually use 5-7 drops of oil at a time. I apply it twice, 6-10 hours after the first layer, I give the second layer of oil. Then I wait untill it is completely dry or more (1-3 days or more). The rubbers will preform best after a 5-7 days.
In case of some rubbers I also oil the topsheet, because it restores some of the grip. I only 1 drop or less in case of softer topsheets. With more rigid topsheets like MX-P I give it 2-3 drops of oil, which makes the topsheet a bit bouncier and lively.
From what I have read falco is a good booster, seamoon also.