You're dealing with two questions here really dude. What shields should do against scythes and what they should do against cloaks.

Against scythes you have dirtbag in chokepoints (the ramps) for scouting, outlaw/multiple llts in your base for damage control, roach as best you can, also build your base to be boxed in by solars if you reasonably can.

Against cloaks, your biggest problem is that they hold the speed advantage and as such, can raid and expand more freely. If you are going to go shields, I would always suggest recon commander to speed up your expansion which will otherwise be too slow. Early game you want to pressurize the cloak player with as many bandits as possible - in their territory, not yours. Remember that the bandit has a range advantage and has a bigger say in engagement than glaive in small numbers. If you can hold them down like this, their riot unit will come and you will have made it out of the raider phase, hopefully with more income than them. It's often a good idea to deploy your bandits via places you intend to expand to, just for a safety sweep.

Send many, and early. Cost for cost the bandits will beat the scythes - particularly if spread out nicely. Remember that they take a good amount of metal and time to make compared to your bandit, which gives you breathing space and the opportunity to snowball.

I think Scythe makes defense impossible for both the scythe player and their adversary (unless the adversary is one of those few factories with reliable counters, such as spider, rover, jump). Heavier raiders need to spread out to comb for Scythes, which gives an equal cost in Scythes enough opportunity to kill them one by one with local superiority.

But scythes themselves suck at direct combat, so can't really defend against massed raids either. It's a game where every button is attack.