There is an informative video on how to fill the fore-end with resin on YouTube. This is for a Savage stock, but the method and end result is identical for the Hogue.

The ONYX epoxy sets in 90 minutes.

This part of the stock uses 120 ml of epoxy to fill, and the epoxy has a relative density of just over 1, so the stock is now 120 grams heavier. If you want extra weight, just mix in the required weight of lead shot before pouring.