Liquid chalk may be an option; back strength dos play into grip as well as already said.
The hook grip works and it is painful when initially employed; Oly lifters, strangely, restrict the use of the hook grip purely because it is painful, so it's also dropped in favour of conventional grip during some of their training, to some degree, and saved for the platform lifts and some lifts during training, to permit the thumb to tolerate it. There is also a particular manner in which to pull/grip the thumb which the following site will probably address in more detail...
Here's a site that may go more in-depth and understand more about the hook grip than may be the case with members here:
Olympic Weightlifting: Catalyst Athletics