Decided to post my reply to your PM in here as well, just in case anyone reading this also finds this useful:
Hi Francis,
No problem mate. Yeh unfortunately if you have dry areas as you have experienced, then the entire laminate will be riddled with porosity and sanding the laminate will expose it - as you've experienced. The best way to keep the dust out of those pinholes is to wet-sand instead, so that the dry dust doesn't pack into the porosity. Then it's much easier to clean out.
Your layup sounds fine, there's nothing wrong with that layup. Interesting Gurit have advised you to drill more holes - I use Gurit perforated foam core in 24ft yachts without needing to drill extra holes. What resin system are you using?
MTI hose is a great product, but I do advise not treating it any differently to a regular infusion - it's just there to give you an added layer of security. Follow Easy Composites tutorial video on infusing the Kevlar ice sled. It is important when you do your canoe that your feed line setup is optimised. Don't infuse any further than 500mm - if you do, not only do you risk dry spots, but the vacuum acting on the flow front gets too high and you will have porosity (this is likely what has caused your dry spots near your MTI hose). So break your infusion down into smaller sections no bigger than 500mm. Easy Composites video touches on this, and you can look up videos of 'Staged' infusions as well.
As far as timing on clamping off your resin feeds goes, again look at the Easy Composites tutorial vid for guidance. Yes - I leave the resin feed open for a time after the resin has reached the outlet for cosmetically important parts. The amount of time depends on the size of the infusion - for something the size of a canoe, I would suggest somewhere between 2-5 minutes. So once the resin has completely wet out the laminate and reached your MTI hose, wait 2-5 minutes, and then clamp your resin feed lines. Whether you shut your pump off for this or leave it on is entirely irrelevant - the pump isn't doing anything once the infusion is complete, but it may give you a small layer of protection if you happen to develop a leak right as your finishing the infusion. This is somewhat less the case when using MTI hose though, as the hose effectively seals off as soon as the resin reaches it.
As for your bridging problems, there's really no tricks to this - it's an experience thing. You will work it out as you get more experience. But you need to be taking your time when you pull that initial vacuum and position everything. Pull a partial vacuum, just tight enough for the bag to be pressing against your materials but with enough slack that you can easily slide things around. Starting from the deepest point, and with plenty of bag, press the materials down into the corners. You don't want to feel any sponginess, your bagging stack should feel very firm when you press the corner. If you feel or see the material move or bounce back as you press it in, then you've got bridging. If you need to, let off some vacuum so you can move the materials around easier and press them right into the corner - then pull a higher vacuum while you hold the materials there. Repeat this process as much as you need to to get all of the material into all of the corners until you can't feel any sponginess at all anymore. One bit of bridging is enough to ruin an entire laminate, so be very methodical and don't get impatient. After a bit of time under consolidation, the materials will start to take a pre-form and stay where you want them too, so don't worry when you need to let the vacuum off to sort out another area of bridging. This process can take hours on a large and complex layup, so just take your time with it and you'll get there eventually.