I posted a guide on Steam forums: "Ten Tips for Terminators". It includes some thoughts on Blocking Entry Areas. You can find the full guide here, if you want to take a look:
"TIP #8 BLOCKING ENTRY AREAS
Some maps will make it hard to utilize this, but you should always be mindful of the possibility.
Blocking an Entry Area at the right time, could turn the tide of battle.
From what I heard, this is not covered well at all, in the tutorial, so here is the official rule:
If a Marine is six, or fewer, squares away from the square next to the Entry Area, Stealers and Blips cannot enter the map on the turn they are placed, they must Lurk, for at least one Turn.
On the next Turn however, they may enter as normal. Count by the shortest possible route, ignoring facing, doors, flames, intervening models or Blips.
If a Blip or Stealer was already Lurking in the Entry Area when the Marine moved to within six spaces, it can enter play immediately. It does not have to Lurk an additional Turn because the Marine showed up – he’ll just have to take his chances.
Important: Blips are never forced to Lurk for more than one Turn. They can always move on the second or subsequent Turns (though they don’t have to move if they don’t want to).”
This not only enables you to delay the Stealer reinforcements. Depending on your opponent, and the nearby layout of the Hulk, you can use this to create “reinforcement-decoys”.
Because one thing is certain: If you block an Entry Area, the Stealer player will surely put Blips there - restraint, is hardly the way of the Xenomorph.
But he won’t be able to move them in, until the next turn. That’s when you get out of the way, pull up the Flamer, and let him hose that burning promethium towards the Entry Point, all night long, giving your other Marines time to move up."