The quickest way to get the Blockbuster is by dashing into it. This can be done by Sweet Science and Roly Poly. Other heroes can replicate this by using speed pads at the right time, although this is very hard to time correctly.

The 2nd best way to get the Blockbuster is by being one block under it while spamming your jump button. You will often find higher level players using this strategy when they have the oppurtunity as it is easy to perform, but still gets you the Blockbuster most of the time.
If you are more than one block under it will take you more time to get it, making it easier for someone else to steal it from you.

Another good way to get it if you are unable to make it under, is to sprint into it. Make sure you don't sprint too early as it will make you sprint on top of it.

Should be obvious why this is a bad idea.

Although it is good to know the quickest way to get it, it does not mean that you will always get the boost. A lot of times the way you get the drop itself is not important, as the outcome is decided by the fights leading up to it.

Thank you Joshmesh for helping.

PS: I might update this guide in the future to include how to prepare and fight for it, but for now it is only about getting the boost.