How to maximise single sales?

Hey all.
New to this game, nice to see something similar to Project Rockstar after all these years.
Just wondering how to maximise single sales - the profits per day are just about paying the band's wages with a bit left over.  
I've picked members with high stats, but it seems sales are low.  I'm assuming we get better quality singles if we write longer?  Also, are secondary skills a thing here like they were in PR?  So, if you have a solo pianist act, you'd be advised to also have someone with high keyboard skills alongside the piano.
Max out every members skills (100 all) Write longer songs (3 days) promote (personally I recommend promote your new record for 5-7 days) then write a 3 day song & keep doing that cycle.. honesty the longer you play, you’ll see what fits you.
For the purposes of singles, only skills that matter are instrument skill, writing and recording. To maximize single rating, make sure you maximize the number of musicians in your band and that all of their instrument skill, writing skill and recording skill are 100. And write a song for 3 days if you’re trying to make the best single.
The only other factor for single sales is fame - which is always going to start as 10% of the band fame (plus any modifiers you have from the shop). 
You will have to buy most of the items in the shop as well to maximize a singles rating and starting fame.