X-Head Porting....

Heat and steel wool can make red rust turn blue/black. Red rust isn't much of a problem unless the parts get repeatedly exposed to moisture (hydrating red rust makes it increase in volume and flake off, eventually 'eating' the metal apart).

I run parts in the dishwasher (no soap! it's caustic and will cause pitting) and ensure the temp of the water and dry cycle is maxxed. Run a 'short wash' (longer wash cycles and longer dry cycles bring back the risk of additional red rust) and keep checking during the dry cycle - if you start to see reddish colors or red pimples, time to pull the parts. It doesn't work so well if there's already oil on the red rust though, so de-grease prior to the wash cycle.

Once pulled from the washer, rub with some steel wool (#00 or #000 - #0000 is too fine for my liking, just shreds on coarse parts) and buff up any areas that are crusty, and otherwise leave the rest alone. Then shower it with some WD40 to prevent further red rust. The WD will also help catch some of the iron dust and not make *quite* as big of a mess.

Obviously married men aren't allowed to try this process.

While grinding (or doing anything with compressed air), use a dust mask or respirator. That metal dust gets nasty in your nose...

Since you're not looking to alter the characteristics of the heads, just stick to your cleanup goals and go for it. Burrs might be a little much if all you want to do is clean up and remove casting flaws though. Burrs will 'bite' metal more and can be tougher to control and since they can leave a rather rough surface it gets tough to see where you've 'cleaned' and where you've actually removed a ton of metal. For your project, I'd be using coarse sanding rolls (36-60 grit).. but that's just me.

Undoubtedly you've read the other threads on porting and know that the real differences for modest amounts of work comes from the roof and the sort side. Without a bench, I'd stay away from the short side. The pushrod pinch isn't worth much until you've done a lot of other port work. But if I were you and wanted to feel like you actually 'ported' rather than 'cleaned' the ports - I'd raise the roof a bit and follow some of the info on this and other sites. Go for the low hanging fruit knowing that you won't be able to deliberately fine-tune things like the common wall and short side without a bench. But you can port-match, de-hump, smooth out, raise the roof, blend the bowl and clearance the guide bosses and know you're not likely to be going backwards at all. Just keep your tools away from the floor of the short side - it's ok to buff it a bit though, but it's tough to reach anyway so leaving it as-is other than slight blend of the bowl is just fine.

Also, if I were you, I'd treat these heads as if you're going to rebuild them and put them onto your engine and then do exactly that. If you port the heads which are currently on your engine, they're going to need rebuilt and valve-jobbed anyway (hard to do much grinding without at least nicking the seats, even accidentally!).
Might as well make these heads work for you - and then you can keep your 'virgin' ones to go back to if you don't like the results of home-porting.

Grinding iron takes a while, so you'll have plenty of time to hunt for super cheap deals on valves, springs, retainers and keepers - maybe even work with a local shop who might cut you a deal to install some sleeve guides, valve job and some help on final assembly.