IDK what's best & it's sorta a trick question/YMMV as you discover what's needed as you go, but I've definitely had some real 240 problem children, proceed methodically with 'abundance of caution' as they say w/the average crusty 240 octopus/medusa.
Having some really good penetrating oil, a wire wheel for crustier cars, a heat source (temp controlled heat gun with an attachment to wrap around the brake hose w/female recepticle & metal hose ferrule to be discarded for the fancier among you, or little compact torch applied cautiously), & good line wrench/crows foot wrench & some spare short strut hard lines & lines to the junction on the x-member from a mid-cycle car that they come off of easily might be wise?
If you take those prep steps & the hard lines are on hand, it'll probably go smoothly, corner at a time, as 2manyturbos sez.
-Flush with clean fluid first (motive power bleeder makes this easy, just don't allow it to run dry and blow air thru the system!
), verify all bleeders flow & aren't a total ball of rust or don't snap off with the existing lines.
-Pump up/extend rear caliper pistons as much as you dare (fully worn out rear pads you have laying around?).
-Stick on brake pedal with brake lamp fuse pulled (replace at the end of the procedure) / introduce as little air as absolutely possible. Usually the diameter of the lines is such that if the master's any good, nary a drop is lost per line changed.
-Corner at a time or even just 1 circuit in each corner caliper at a time, checking that you have a pedal after each hose/corner diligently/cautiously gingerly pumping up the pedal massaging it until the pads make solid contact without dragging an old MC seal/piston over an unused portion of the MC bore.
-Send no air back to rear prop valves under any circumstances if at all possible or else you're in a world of hurt / (smokey, you're) 'entering a world of pain.'
-Front corners/1 circuit ea first, checking gingerly, usually...it's tedious, baby steps, keep it wet with no air sent back or into the junction, lose as little fluid as possible!
-Rears last (if at all for hoses, I rarely bother with the rear hoses on cool weather 240s if I don't know how long I plan to keep the car & just junkyard replaced front hoses...rear hoses that close up is more of a 700 thing or MUCH more a 140 original hoses thing (they swell up & close or have liner problems moreso than 240 hoses), compress rear caliper pistons back/reinstall near new rear pads to push the air forward at each rear caliper, but because you flushed it with clean fluid you shouldn't be sending gross fluid/rust crap into the master if you dun-did-it-right / did your homework right!
-Reverse bleed the master a couple times at the very end as needed if you're fortunate enough to have an assistant.
-Gingerly massage brake pedal with minimal travel until pistons make contact again/don't drag the master piston over the whole master cylinder bore.
BTDT a ton of times with various crusty 240s to replace raspy soft hoses with good results/no surprises, but you have to be really careful.
Particularly up front, tho I'm lazy and don't always replace rear hoses as they tend to last a long long long time (comparatively) on the last of the 240s in a mild no UV rainy climate, but the fronts the jackets get all hammered out & flexed around a lot more in their sorta 'elevator cable' shape to the strut eyelets....why they didn't make those eyelets stainless or alloy & removable god only knows...I guess BNE has a kit for that/cute little clasp for coilover kool-aid drinkers...or just people that have molested cars even (I've seen hacks cut the eyelets open).
I wouldn't know/don't lower or lift my mid size car; it is what it is & I live with those stupid closed eyelets on the strut housing if I have the misfortune of having to replace a strut or strut insert; I'm happy to be able to get ~1 ton pickup service out of something the size of a defective by design compact pickup that fits in a 7' high door single car old Portland skinny horesless carriage/horse carriage/model A or Model T garage/shack, even if its Swedish/has expensive parts (but conservative defacto ~1967-1993 model run like a Jeep Grand Wagoneer/J-series truck, SAAB 99/C900, Jeep XJ (84-02 (& longer outside the USA) or 73-91 suburban or ~81-97 ford F-series pickup, with most/many parts basically compatible)
Good luck to ya on the dual diagonal medusa.
The line junction/failure switch is really the bugger to replace on the 240 & avoid sending air back thru the prop valves (which are starting to fail by now/prevent fluid from passing/one rear caliper sometimes refuses to bleed & no other cause can be diagnosed/found & they're not really cheap or 'rebuildable' like the 140/disc brake 1800 pre-planned-obsolescence adjustable prop valves.
I like the design of the 140/earlier 240 line junction/failure switch in theory, but in practice, the leak-proof junction & reservoir float switch is kinda the long game option.
Interestingly, they don't go bad much in the 140 or earlier 700 non-abs cars that use same part as the 240.
The chinesium cheap failure switches/line junctions or the ones in the blue box aren't worth installing, now.
But with the OE line junction, it seems to last well if all the calipers move equally freely/well/rotors don't pulse & fluid is clean.
Seen some on well maintained cars that are super crusty with undercoating on them.