I use a length of airline tubing (I prefer the silicone stuff) and an adjustable pinch valve. Put the new fish and all its bag water in bucket #1 on the floor. Fill bucket #2 with an amount of water from the quarantine tank such that if all of it was added to the first bucket, it wouldn't overflow. Set bucket #2 higher than bucket #1. Put one end of the tubing in bucket #2 and the other in bucket #1. Start the siphon (I use a syringe w/o a needle). Adjust drip rate with pinch valve.
When most of the water has siphoned into bucket #1, test the TDS and compare it to the tank's water. If it's not within 5%, discard all but the minimum amount of water from #1 and fill #2 with more tank water. As before, don't put so much water in #2 that it would overflow #1 if it all siphoned into #1.
Repeat above until the TDS are within 5% then net the fish out and add to tank. Discard water in #1.
I often put a towel over bucket #1 to keep the fish calm and from jumping out.
This process can take hours but I never lose new fish. It eliminates the possibility of gill damage due to TDS (osmotic) shock. I've noticed that properly acclimated fish will act normally within hours rather than hide for the first few days. I've added small clown loaches that were acting normal, rummaging around looking for food the first day rather than hiding (which is what injured fish do).