Sir Richard C. Jebb, Commentary on Sophocles: Trachiniae

ἔβαψα. The notion of a “φίλτρον” in the form of an unguent was a familiar one: thus in Eur. Hipp.516Phaedra asks the Nurse, “πότερα δὲ χριστὸν ἢ ποτὸν τὸ φάρμακον”;

προσβαλοῦς᾿, ‘with application of everything that he directed,’—i.e., applying the philtre to the robe with attention to all the prescribed details. From vv. 680—687 it appears that Nessus had said more than she repeats in 572—577. He gave “θεσμοί” (682), precise instructions.—This is better than to understand, ‘with all the additions that he enjoined’ (schol. “καὶ ἄλλα τινὰ συμμίξασα”): though it may be supposed that the coagulated blood, before being applied to a large surface, was diluted with water. (Schneidewin explains the word by Apollod.2. 7. 6“τόν τε γόνον ὃν ἀφῆκε κατὰ τῆς γῆς καὶ τὸ...αἷμα συμμίξαι”.)— Not, ‘with observance of all that he said’<*> as if “νῷ” (or “νοῦν”) were understood. See on 844 “προσέβαλε”.