You have to scrap off the Red varnish.
Like Danny said the coatings used on the inductors will not make a connection or very week connection if you do solder then and get the inductor HOT enough to melt the coating.Which may reach a temp so hot it will damage a capacitor.

I just personally scratch every inductor to make the best connection.You will find almost every inductor has some kind of coating thin or thick to prevent oxidation till this inductor gets used by the end user.
Now separate crossover boards. Personally I like this choice as I learned several years ago.If say a few months after you order a GR kit you would like to add Sonicaps to the tweeter crossover.(simple just remove the tweeter crossover)
Then say another few months you get some coin.Now you would like to put in Mills resistors with Platinum bypass caps.(simple just remove the tweeter crossover)
By doing the crossovers for 2-3 ways separately it gives easy flexibility for upgrading each crossover network later down the road very easy.