Home Improvement Questions? Ask a Handyman for Answers
The best product I have come across is made by USA Insulations, they offer a full range of products, both in terms of quality, cost and application.
This includes spray on products which can go on external walls direct then you install your drywall over the top, through to what I would think you should do - injection based foam where you construct the void by building the internal dry all then inject foam into the void.
Have a look at the website here.
I would I would just be inclined to re-drill the holes as its only a foam substance your drilling through, and probably quicker than fitting tubes through the weep holes, however with this type of product your have insulation which is water resistant and the thermal properties wouldn't allow much air to circulation anyway, so should be protecting the timber frame from moisture.
If you plan to retain the fibreglass insulation then yes you will require a new weep hole, as the foam is a moisture barrier so wouldn't let air from the weep hole circulate.
Personally I would look to replace all the insulation with the foam, you will improve the thermal efficiency significantly.