If you want to get good results from liking. Use the "Date upload in the last hour" option. This means, the user is probably still online. Play / like the track, and chances are it will be noticed by the user.
Likewise "track upload in last day" means the user is still active on soundcloud (i.e. didn't upload the track 2 years ago and not been on since)
Also, make use of the "USER ONLINE" option, granted, you will skip over most the search results, but as they are not online, it doesn't really matter. Instant acknowledgement
If you have a highly targeted list of tracks, you can now use the Track Comment feature to
play / like / follow the user before commenting on the track. Really hammer home the interaction with the user.
Again, for a HIGHLY targeted list, PMs are great. Usually can get 80%+ response rate.
The above commenting ideas, DO NOT WORK with blanket spam.
You cannot send many PMs before you get a warning then a 24 hour ban (or more). So go easy. REALLY target users who are currently active on soundcloud / into your genres etc leave a 1-2+minute pause between all, use the tokens to personlise the message. BUT KEEP NUMBERS DOWN.
Don't be lame and say
But tell them you "Hey, I like their tracks", give encouragement, "Hey, keep up the good work." make them feel good "have had your track on repeat". They will go check out your tracks and more often than not send you a replyhi, check out my tracks
Track comments are not as restrictive, but still do not blanket post comments, otherwise you will get a temp ban.