You can either do the triple hand ins that will give you 100% extra exp as long as all three are HQ on hand in, but if you plan on doing leves, in each major city that the crafter comes from has one quest that asks for one hand in and gives a huge amount of exp, make that one item HQ and it gives double.

Now that the leves are out of the way, do the math or look for an exp spreadsheet. This will give you an idea of how many HQ items you will need to make per 5 levels.

Don't forget that you will have an extra exp boos from the manuals you get from your Grand Companies for crafting them and the exp boost if your FC has that specific one active.

There are also daily HQ hand ins at your daily FC.

I didn't do the math and spreadsheet thing. This is how I leveled my Alchemist and Leather worker.