This would be my second repair that I will be doing. First repair I didn’t care to much because it was an old used board. This repair I care a lil bit more because it’s on my new shortboard.
As for the hotcoat do I add styrene resin to make it ez to sand? Does it matter what kind of styrene or can I add any type of styrene?
TIA. 
Styrene is a thinning agent. If you’re mixing hotcoat using lam resin, you add sytrene + surfacing agent to get proper flowability and hardening. Check the archives for the right proportions. If you’re using pre-mixed sanding (hotcoat) resin, you don’t need to add anything.
Lam Resin + (Styrene + Pure Paraffin Wax) = Hotcoat Resin
which simplifies to,
Lam Resin + (Surfacing Agent) = Hotcoat Resin
Where the ratio of Surfacing Agent to Catalyst is 2 to 1 respectively…
Simplifies to,
Go buy some Hotcoat resin if it is one ding you are doing.
Or,
Cancel out the Hotcoat resin,
And,
Use SolaRez as a final topcoat as it is kind of sandable.
Can you guys recommend a place where I can buy either hotcoat resin or SolaRez online for a good price? Thanks for your help! =)