I kind of rotate, using synthetic orchid powdered fertilizer one week, then worm tea, then plain water, etc. and have had pretty good results. Of course it's impossible to say that I'm getting the best possible.

I feed with every watering at 10-20 ppm N (figure out how much that is for your fertilizer using Ray's calculator; link posted earlier). My plants really like Neptune's Harvest fish/seaweed, but I find it feeds a lot of algae as well. So I alternate with K-Lite and even some PlantProd 25-10-10. But keep it really low - 10 ppm N is less than 1/10th the recommended strength on most commercial fertilizers - after all, fert manufacturers won't make any money by telling you to use less of their product.

The fertilizer number e.g. 10-10-10 is expressed as percentages. The first number is the percentage of nitrogen. So a 10-10-10 fertilizer at 100 ppm is giving 10 ppm of nitrogen.

David, I disagree with you there. A lot of salts also contain waters of hydration, even when they appear to be completely dry. These bound water molecules add to the weight of the fertilizer (and the numbers are as a % of weight for each of the 3 main elements), but they don't add to the ppm. So most likely, 100 ppm of a commercial 10-10-10 fertilizer will contain more than 10 ppm of nitrogen.

With liquid fertilizers, water plays an obviously bigger role. Most liquid formulations are 40-60% water; organic fertilizers are even more dilute. However, the three N-P-K numbers still refer to the % of the bottled product, not just its dry weight. And with organic fertilizers, some ingredients are not dissolved salts, so they won't register on the TDS meter. However, they still contribute to plant nutrition.

If you take a 10-10-10 fertilizer and dissolve 0.1 gram of it in a liter of water then you will have a solution containing 10 ppm of nitrogen.

I feed my collection(couple of hundred I think) with Akernes Rain mix at 1/2 gram litre at every watering, no flushing, no hassle. Comes out about 550-600 microsiemens, I don't know what root burn is.

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Do you feed with this concentration on humid roots?
Living in Belgium you will easily understand that I have already used RainMix fertilyser with rain water. I am sure that used at 0.5 gr / L roots are burned. I am not the only one to have made the experience. But on already wet roots or non-displayed to light maybe to feed at this concentration it's possible. Please, explain me exactly how you do because I am not the only one be to be interested. This is a subject about which I have discussed many time with Kenneth. Many thanks in advance.

I use Rain Mix at 0.5g/L on Masdies with no problems. However I keep my masdies always moist, so the roots are rarely completely dry when water. It could be different on completely dry roots.

I used to use a different fertiliser and my mixing rate worked out at a higher concentration. I had no problem with that on Masdies either, though I didn't use it with every watering.

Without reliable data you can never be sure.
I watered my Masdies only with rainwater. I constantly check the electric conductivity with a meter. Pure rainwater in the city measures 15-60 microSiemens. I add fertilizer for Masdies up to 300 microSiemens. If kept constantly more or less humid and in growth, the plants can stand a higher concentration. Mounted plants and dry plants need lower concentration.
To the contrary Cattleyas get 600- 1000 microSiemens in summertime.
Any balanced fertilizer suited for orchids suits for Masdies. I would not calculate concentration but measure. I recommend to avoid well water in the long run. I strongly recommend to buy a meter.
Happy growing!