If I have anything to add as a factoring resources, it's that my students get way more multiplying polynomials questions right if they multiply the polynomials in a repurposed Punnet Square. I don't feel at all guilty about this for two reasons:
1. My strongest students ignore the box since they can do the multiplication much more quickly without it.
2. Me weaker students LOVE it, since it keeps them from making sloppy mistakes.
I like it because it reinforces their geometric intuitions about area and makes a nice connection between algebra and geometry. The downside is that it doesn't really do a great job setting them up for factoring, but we'll see how that goes.
I'm not sure whether to teach them factoring by grouping or whether to just focus on getting them the ac/a+c intuition for trinomials where a=1. The advantage of teaching them grouping is that it'll make Alg2 much easier for them. And some teachers swear by the grouping.
Here's a rolling post on factoring resources:
DEFENSE OF FACTORING
SOME TRICKS THAT MIGHT BE USED TO MOTIVATE IT
USING GROUPING TO FACTOR TRINOMIALS
SOME FACTORING GAMES/WORKSHEETS