Shaun,
With the focuser sticking, the best thing would be to pull it apart and remove all the old grease. This will be causing the problem.
Don't just replace with any old lubricant, the reason behind this is that certain lubricants will either melt in the heat or bind the focuser when cold.
I use "Superlube" this was recommended to me by Don Whiteman from Bintel.
I've used it on all my scopes with great success.
