About shelac... Great stuff but unless you have a lot of ventilation in the basement, Rap, you may end up in the hospital.... It's so nasty that in order to purchase it in some places you'll have to sign a statement that says yopu are aware of it's toxicity...

As fir filling the groves, that 3/8 inch knap should deliver the paint into them but if yer gonna fill 'um, get yerself some rubber gloves so you'll have a finger left after the job... The latex ones won't cut it...

Bobert