Depending on what you are doing, this is how I'd run it (and have run it)
On a house, I've had an earth wizard make all the windows extremely hard. This was an easy block/2 for armour.
On a weapon, I'd use skill replacement or just a maneuver to place appropriate aspect: Magically sharp(sword); Incredibly durable (armour) etc..
For straight up armour effects, It might be crafting or conjuration but I'd use resource skill replacement. So it'd be like buying armour/weapons.
Or craft skill replacement...whatever...the resource table is much more detailed though, so I'd use that to determine required shifts.
You want the equivalent of a Kevlar vest, it'd be a ritual of "X" (where "X" is the cost) + duration. If you wanted it to be the equivalent of riot gear, It'd be the price of riot gear + duration, + extra shifts if you wanted your riot gear to look and feel like regular clothes (since that would be the equivalent of buying super high-tech/secret military gear.) There wouldn't be extra difficulty for "availability/legality" or whatever, since ritual lets you bypass those kinds of restrictions.
I'd do the same thing for a gun that shoots electricity, I think. Choose a weapon type, cost it out, add some extra shifts because it's shooting electricity instead of bullets.
When duration wears out, the item breaks and needs to be fixed/recharged. Meaning, you need a new ritual.
Thaumaturgy makes my head hurt.