Start with the rough mix
Send a current stereo bounce that includes all the parts the guitarist needs to react to. It does not need to be mixed professionally. It needs to represent the arrangement accurately enough that the player understands the vocal, groove and harmonic context.
Include the session facts
Send BPM, song key if known, sample rate, bit depth and any tempo changes. If your DAW supports markers or you have a written arrangement map, include section names and bar numbers where possible.
Explain function before tone
“Warm electric guitar” can mean many things. It is more helpful to explain whether the part should create pulse, widen the chorus, answer the vocal, add tension, support harmony or become a hook. Tone can then be chosen to perform that function.
Use references carefully
A reference track can explain feel, register or production density. Do not assume the remote guitarist must copy a specific copyrighted part. The goal is to understand the musical role and create something appropriate to your song.
Professional delivery should line up immediately
Returned WAV files should normally be consolidated from a common start point so the producer can drag them into the session without manually placing every phrase. Clear filenames matter. If a clean DI is useful for re-amping or flexibility, agree that before recording.
Revisions should follow the original brief
One reasonable revision round is common when the project scope is clear. A revision means adjusting the agreed part, not changing the entire creative direction after recording. If the brief changes substantially, treat that as new work rather than hiding it inside unlimited revisions.
The best remote players interpret
The benefit of a seasoned session guitarist is not just reliable audio files. It is the ability to hear what is missing, avoid what is already crowded and return a part that belongs to the record with minimal explanation.
Next step
If this is the problem you are trying to solve in a current song, you do not need to wait until the project is polished. Send Sven the demo and explain where the decision feels unclear.